HK1033800A - Channel structure for communication systems - Google Patents

Description

Channel structure for communication system

Technical Field

The present invention relates to a channel structure of a communication system.

Background

As one of several communication techniques that facilitate the existence of a large number of system users, a Code Division Multiple Access (CDMA) modulation technique is used. While techniques such as Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) are well known, CDMA has significant advantages over other such techniques. The use of CDMA techniques in multiple access communication systems is disclosed in U.S. patent No. 4,901, 307, entitled "spread spectrum multiple access communication system using satellite or terrestrial repeaters," which is assigned to the assignee of the present invention and is incorporated herein by reference. The use of CDMA techniques in multiple access communication systems is disclosed in U.S. patent No. 5,103, 459, entitled "system and method for generating signal waveforms in a CDMA cellular telephone system," which is assigned to the assignee of the present invention and is incorporated herein by reference. The CDMA system may be designed to conform to the "TIA/EIA/IS-95 mobile station-base station compatibility standard for dual-mode wideband spread spectrum cellular systems," hereinafter referred to as the IS-95 standard. Another code division multiple access communication system includes a GLOBALSTAR communication system for global communications using low earth orbiting satellites.

A CDMA communication system is capable of transmitting traffic (traffic) data and voice (voice) data on the forward and reverse links. A method of transmitting traffic data in fixed size code channel frames is described in detail in U.S. patent No. 5,504, 773 entitled "method and apparatus for formatting transmitted data," which is assigned to the assignee of the present invention and is incorporated herein by reference. According to the IS-95 standard, traffic data and voice data are divided into traffic channel frames having a duration of 20 milliseconds. The data rate of each traffic channel frame is variable and can be as high as 14.4 Kbps.

In a CDMA system, communication between users is carried out through one or more base stations. A first user at a remote station communicates with a second user at a second remote station by transmitting data on a reverse link to a base station. The base station receives the data and may route the data to another base station. The data is transmitted on the forward link of the same or a second base station to a second remote station. The forward link refers to transmission from the base station to the remote station, and the reverse link refers to transmission from the remote station to the base station. In an IS-95 system, different frequencies are assigned to the forward link and the reverse link.

The remote station communicates with at least one base station during a communication. A CDMA remote station is capable of communicating with multiple base stations simultaneously during soft handoff (handoff). Soft handoff is the process of establishing a link with a new base station before breaking the link with the previous base station. Soft handoff minimizes the chance of a dropped call (drop). Methods and systems for communicating with a remote station through more than one base station during a soft handoff are disclosed in U.S. patent No. 5,267, 261, entitled "mobile assisted soft handoff in a CDMA cellular telephone system," which is assigned to the assignee of the present invention and is hereby incorporated by reference. Softer handoff is a process where communication occurs over multiple sectors served by the same base station. A softer handoff procedure is disclosed in co-pending U.S. patent application No. 08/763, 498 entitled "method and apparatus for handoff between sectors of a public base station" filed on 11.12.1996, which is assigned to the assignee of the present invention and is incorporated herein by reference.

With the ever-increasing demand for wireless data applications, the need for very efficient wireless data communication systems has become more and more apparent. An exemplary communication system for optimizing data transmission is described in detail in co-pending U.S. patent application No. 08/654, 443 entitled "high data rate CDMA wireless communication system" filed on 28.5.1996, which is assigned to the assignee of the present invention and is incorporated herein by reference. The system disclosed in U.S. patent application No. 08/654,443 is a variable rate communication system capable of transmitting at one of a plurality of data rates.

The obvious difference between voice traffic and data traffic is that the former requires a common grade of service (GOS) that is fixed for all users. Typically, for digital systems providing voice services, this translates into a maximum allowable value for a fixed and equal data rate and error rate relative to voice (speech) frames for all users, regardless of link resources. For the same data rate, users with weaker links require higher resource allocations. This results in inefficient use of available resources. In contrast, for data traffic, GOS can be user specific and can be a parameter optimized to increase the overall efficiency of the data communication system. The GOS of a data communication system is generally defined as the total delay incurred in the delivery of a data message (message).

Another significant difference between voice traffic and data traffic is that the former bears the need for a strict fixed delay. Typically, the overall one-way delay of a speech frame must be less than 100 milliseconds. Instead, the data delay may become a variable parameter used to optimize the efficiency of the data communication system.

The parameters that measure the quality and efficiency of a data communication system are the total delay required to deliver a data packet (packet) and the average throughput (throughput) rate of the system. The total delay does not affect data communication as much as it does voice communication, but it is an important measure for measuring the quality of a data communication system. The average throughput rate is a measure of the efficiency of the data transmission capability of the communication system.

Communication systems designed to optimize the transmission of data traffic and voice traffic need to address the specific needs of both services. The present invention is directed to a channel structure for facilitating transmission of data and voice traffic.

Summary of The Invention

In one aspect the present invention provides a channel structure for a communication system, the channel structure comprising: at least one fundamental channel for transmitting traffic data, voice data, and signaling; a supplemental channel for transmitting traffic data; and a paging channel for transmitting paging messages.

In another aspect the present invention provides a transmitting apparatus for a communication system, the apparatus comprising a transmitter for: transmitting traffic data, voice data and signaling in at least one fundamental channel; transmitting traffic data in a supplemental channel; and transmitting the paging message in a paging channel.

In yet another aspect the present invention provides a receiving apparatus for a communication system, the apparatus comprising a receiver for: receiving traffic data, voice data and signaling transmitted in at least one fundamental channel; receiving traffic data transmitted in a supplemental channel; and receiving a paging message transmitted in a paging channel.

The present invention also provides a channel structure for use in a communication system. The communication system includes two sets of physical channels, one for the forward link and one for the reverse link, which are utilized to facilitate communication of various logical channels.

The present invention may be implemented in two sets of physical channels (one for the forward link and the other for the reverse link) to facilitate communication of logical channels. The physical channels include data and control channels. In an example embodiment, the data channels include fundamental channels for transmitting voice traffic, data traffic, high speed data, and other overhead (overhead) information, and supplemental channels for transmitting high speed data. In this example embodiment, the forward and reverse traffic channels may be released (released) when the remote station is idle to more fully utilize the available capacity. The control channel is used to transmit the control message and the scheduling information.

Preferably, the traffic channels include fundamental and supplemental channels. The fundamental channel may be used to transmit voice traffic, data traffic, high speed data, and signaling messages. The supplemental channel may be used to transmit high speed data. In this example embodiment, the primary and supplemental channels may be transmitted simultaneously. In this example embodiment, to improve reliability (especially for signaling messages), the fundamental channel may be supported by soft handoff.

Preferably, the supplemental channel is transmitted at one of a plurality of data rates. This data rate is selected based on a set of parameters that may include the amount of information to be transmitted, the available transmit power of the remote station, and the energy per bit (bit) required per bit. The data rate is allocated by the scheduler to maximize the system throughput rate.

Preferably, the power levels of all base stations in the active set of remote stations are measured periodically during the communication. The delta power levels of the multi-cells (multi-cells) are transmitted to the base stations, which use this information to transmit high speed data from the "best" set of base stations, thereby increasing capacity. In addition, the power levels of all carriers are periodically measured and the delta power levels of the multiple carriers are transmitted to the base station. The base station may use this information to increase the power level of the weak carrier or to reallocate a new carrier allocation to a remote station.

The remote station may operate in one of three modes of operation, including a traffic channel mode, a suspend mode, and a sleep (dormant) mode. The remote station is placed in a suspended mode if an inactive period since the last transmission termination exceeds a first predetermined threshold. In this example embodiment, in the suspended mode, the traffic channel is dropped while state information is maintained by the remote station and the base station, and the remote station monitors the paging channel in a non-slotted mode. Thus, the remote station may be returned to the traffic channel in a short period of time. If the period of inactivity exceeds a second predetermined threshold, the remote station is placed in a sleep mode. In this example embodiment, in sleep mode, neither the remote station nor the base station maintains state information, but the remote station continues to monitor the paging channel in slotted mode for paging messages.

The control data may be sent on a control frame that is part of a traffic channel frame. In this exemplary embodiment, the remote station transmits the data rate and other information requested by the remote station using a control channel frame format that minimizes the processing delay between the time the data rate request is made and the time the actual transmission is made at the assigned data rate. In addition, the present invention provides erasure-indicator-bits for the forward and reverse links, which can be used in place of the NACK RLP frame defined by the IS-707 standard.

Brief description of the drawings

The above and further features, objects and advantages of the present invention will become more apparent from the following detailed description of embodiments of the invention when taken in conjunction with the accompanying drawings in which like reference characters designate corresponding parts throughout the several views and wherein:

FIG. 1 is a diagram of an exemplary communication system embodying the present invention;

FIG. 2 is a block diagram showing the basic subsystems of an exemplary communication system embodying the present invention; and

FIG. 3 is an exemplary diagram illustrating the relationship between physical and logical channels on the forward link;

FIG. 4 is an exemplary diagram illustrating the relationship between physical and logical channels on the reverse link;

FIGS. 5A and 5B are exemplary diagrams illustrating, respectively, the use of inter-cell Δ power levels to control forward supplemental channel transmissions;

fig. 6 is an exemplary diagram of a frequency spectrum of a received multi-carrier signal;

FIG. 7A is a diagram of an example reverse link pilot/control channel frame format;

FIG. 7B is an example timing diagram illustrating reverse link high speed data transmission;

FIG. 7C is an example timing diagram illustrating the use of inter-cell Δ power levels;

FIG. 7D is an example timing diagram illustrating the use of inter-carrier power levels;

FIG. 7E is an example timing diagram illustrating the transmission of an EIB bit;

8A-8B are example timing diagrams illustrating transitions to suspend and hibernate modes and illustrating transitions between operating modes, respectively;

fig. 8C is an exemplary diagram illustrating a case where a remote station operating in a suspended mode transmits a location update message when a new pilot is detected;

9A-9B are exemplary diagrams illustrating a base station initiated protocol transition from suspended and dormant modes to traffic channel mode, respectively; and

fig. 9C-9D are exemplary diagrams illustrating a protocol for a remote station initiated transition from a suspend and sleep mode to a traffic channel mode, respectively.

Preferred embodiments of the invention

I. Description of the System

Referring to the drawings, FIG. 1 illustrates an example communication system. One such system IS a CDMA communications system that conforms to the IS-95 standard. Another such system is described in the aforementioned U.S. patent application No. 08/654, 443. The communication system comprises a plurality of cells 2a-2 g. Each cell 2 is served by a respective base station 4. Remote stations 6 are dispersed throughout the communication system. In the exemplary embodiment, each remote station 6 communicates with zero or more base stations 4 on the forward link at each traffic channel frame or frame. For example, on the forward link, base station 4a transmits to remote stations 6a and 6j, base station 4b transmits to remote stations 6b and 6j, and base station 4c transmits to remote stations 6c and 6h at frame i. As shown in fig. 1, each base station 4 transmits data to zero or more remote stations 6 at any given moment. In addition, the data rate is variable and may depend on the carrier-to-interference ratio (C/I) measured by the receiving remote station 6 and the required energy-to-noise-per-bit ratio (E)_b／N_o). For simplicity, the reverse link transmission from remote station 6 to base station 4 is not shown in fig. 1.

A block diagram of the basic subsystems of an exemplary communication system is shown in fig. 2. The base station controller 10 interfaces with the packet network interface 24, the PSTN30, and all base stations 4 in the communication system (only one base station 4 is shown in fig. 2 for simplicity). The base station controller 10 coordinates communication between the remote station 6 in the communication system and other users connected to the packet network interface 24 and the PSTN 30. PSTN30 interfaces with users through a standard telephone network (not shown in fig. 2).

The base station controller 10 contains a number of selector elements 14, but only one is shown in fig. 2 for simplicity. A selector element 14 is assigned to control communication between one or more base stations 4 and a remote station 6. If the selector element 14 has not been assigned to the remote station 6, the call control processor 16 is notified that the remote station 6 needs to be paged. Call control processor 16 then instructs base station 4 to page remote station 6.

The data source 20 contains data to be transmitted to the remote station 6. Data source 20 provides data to packet network interface 24. The packet network interface 24 receives data and routes the data to the selector element 14. The selector element 14 transmits data to each base station 4 in communication with the remote station 6. In the exemplary embodiment, each base station 4 maintains a data queue 40 containing data to be transmitted to remote stations 6.

Data is sent from data queue 40 to channel element 42 in data packets. In the exemplary embodiment, on the forward link, a data packet refers to a fixed amount of data to be transmitted to the destination remote station 6 within one frame. For each data packet, channel element 42 inserts the necessary control fields. In the exemplary embodiment, channel element 42 CRC encodes the data packet and control field and inserts a set of code tail (tail) bits. The data packet, control field, CRC parity bits, and code tail bits comprise a formatted packet. In an example embodiment, channel element 42 encodes this formatted packet and interleaves (or reorders) the symbols (symbols) within the encoded packet. In the exemplary embodiment, the interleaved packet is scrambled (scrambled) with a long PN code, covered with a Walsh cover (cover) and short PN codes_IAnd PN_QThe code is spread. Providing the extended data toAn RF unit 44, the RF unit 44 quadrature-modulates, filters, and amplifies the signal. On forward link 50, forward link signals are transmitted over the air by antenna 46.

At remote station 6, an antenna 60 receives the forward link signal and routes it to a receiver within a front end 62. The receiver filters, amplifies, quadrature demodulates, and quantizes the signal. This digitized signal is provided to a demodulator (DEMOD)64 where it is provided as a short PN_IAnd PN_QDespread with code, decovered with Walsh cover, and descrambled with a long PN code. This demodulated data is provided to a decoder 66, which decoder 66 performs the inverse signal processing functions performed at the base station 4, particularly the de-interleaving, decoding and CRC check functions. This decoded data is provided to a data sink 68.

The communication system supports data and messaging on the reverse link. Within remote station 6, controller 76 handles data or message transmission by routing the data or message to encoder 72. In an exemplary embodiment, the encoder 72 formats a message in accordance with the blank-and-burst (blank-and-burst) signaling data format described in the above-mentioned U.S. patent No. 5,504, 773. Encoder 72 then generates and adds a set of CRC bits, adds a set of code tail bits, encodes the data and added bits, and reorders the symbols within the encoded data. The interleaved data is provided to a Modulator (MOD) 74.

The modulator 74 may be implemented in a number of embodiments. In a first embodiment, the interleaved data is covered by a Walsh code (which identifies the data channel assigned to remote station 6), spread with a long PN code, and further spread with a short PN code. This spread data is provided to a transmitter within front end 62. The transmitter modulates, filters, amplifies, and transmits the reverse link signal over the reverse link 52 over the air via an antenna 60.

In the second embodiment, the modulator 74 functions in the same manner as the modulator of the exemplary CDMA system conforming to the IS-95 standard. In this embodiment, modulator 74 uses Walsh code mapping to map the interleaved bits into another signal space. Specifically, the interleaved data is divided into groups of six bits. These six bits are mapped to corresponding 64-bit Walsh sequences. Modulator 74 then spreads the Walsh sequence with a long PN code and a short PN code. This spread data is provided to a transmitter within front end 62 that functions in the manner described above.

For both embodiments, at base station 4, the reverse link signal is received by antenna 46 and provided to RF unit 44. The RF unit filters, amplifies, demodulates and quantizes the signal and provides the digitized signal to channel element 42. The channel element despreads the digitized signal with a short PN code and a long PN code. Channel elements 42 also Walsh code map or decover in accordance with signal processing performed at remote station 6. Channel element 42 then reorders the demodulated data, decodes the deinterleaved data, and performs a CRC check function. Decoded data, such as data or messages, is provided to the selector element 14. The selector element 14 routes this data and message to the appropriate destination (e.g., data sink 22).

As described above, this hardware supports the transmission of data, messages, voice, video, and other communications on the forward link. Other hardware architectures may be designed to support variable rate transmission and are within the scope of the invention.

The scheduler 12 is connected to all selector elements 14 within the base station controller 10. The scheduler 12 schedules high speed data transmissions on the forward and reverse links. The scheduler 12 receives a queue size representing the amount of data to be sent and other related information as described below. The scheduler 12 schedules data transmissions to achieve the system goal of maximizing data throughput while complying with system constraints.

As shown in fig. 1, remote stations 6 are dispersed throughout the communication system and may communicate with zero or more base stations 4. In the exemplary embodiment, scheduler 12 coordinates forward and reverse link high speed data transmissions throughout the communication system. Scheduling methods and apparatus for high speed data transmission are described in detail in U.S. patent application No. 08/798, 951, entitled "forward link rate scheduling method and apparatus", filed on 11/2/1997, which is assigned to the assignee of the present invention and is incorporated herein by reference.

Forward link channel

In an exemplary embodiment, the forward link includes the following physical channels: pilot channel, synchronization channel, paging channel, fundamental channel, supplemental channel, and control channel. The forward link physical channel facilitates the transmission of each logical channel. In an exemplary embodiment, the forward link logical channels include: physical layer control, Medium Access Control (MAC), user traffic flow, and signaling. A diagram of the relationship between physical and logical channels on the forward link is shown in fig. 3. The forward link logical channels are described further below.

Forward pilot channel

In the exemplary embodiment, the forward pilot channel comprises an unmodulated signal used by remote station 6 for synchronization and demodulation. In the exemplary embodiment, the pilot channel is transmitted by the base station 4 at all times.

Forward synchronous channel

In the exemplary embodiment, the system timing information is transmitted to remote station 6 for initial time synchronization using a forward synchronization channel. In the exemplary embodiment, the remote station 6 is also informed of the data rate of the paging channel using a synchronization channel. In an example embodiment, the structure of the synchronization channel may be similar to that in an IS-95 system.

V. Forward paging channel

In the exemplary embodiment, the forward paging channel is used to transmit system overhead information and dedicated messages to remote station 6. In an example embodiment, the structure of the paging channel may be similar to that in an IS-95 system. In an example embodiment, the paging channel supports slotted mode paging and non-slotted mode paging as defined by the IS-95 standard. Slotted and non-slotted mode paging is described in detail in united states patent No. 5, 392, 287 entitled "method and apparatus for reducing power consumption in a mobile communication receiver" entitled 2/21 in 1995, which is assigned to the assignee of the present invention and is incorporated herein by reference.

Forward fundamental channel

In the exemplary embodiment, voice, data, and signaling messages from base station 4 are transmitted to remote station 6 during communication using a forward traffic channel. In an example embodiment, the forward traffic channel includes a fundamental channel and a supplemental channel. The fundamental channel may be used to transmit voice traffic, data traffic, high speed data traffic, signaling traffic, physical layer control messages, and MAC information as shown in fig. 3. In the exemplary embodiment, the supplemental channel is used only for transmitting high speed data.

In an example embodiment, the fundamental channel is a variable rate channel, which may be used in one of two modes: dedicated mode and shared mode. In dedicated mode, the fundamental channel IS used to transmit voice traffic, IS-707 data traffic, high speed data traffic, and signaling traffic. In an exemplary embodiment, signaling information is transmitted in dedicated mode in a half-and-burst (dim-and-burst) or blank burst format as described in the above-mentioned U.S. patent No. 5,504, 773.

Alternatively, if remote station 6 does not have an active circuit switched service (e.g., voice or fax), the fundamental channel may operate in a shared mode. In the shared mode, the fundamental channel is shared by a group of remote stations 6 and the forward control channel is used to indicate to the remote stations 6 when to demodulate the assigned fundamental channel.

The shared mode increases the capacity of the forward link. In the absence of active voice or circuit switched data traffic, it is inefficient to use a dedicated fundamental channel, since this fundamental channel is being utilized by both intermittent packet data traffic and signaling traffic. For example, a basic channel may be used to send TCP acknowledgements. To minimize transmission delays in the delivery of signaling messages and data traffic, the transmission rate of the fundamental channel is not significantly reduced. Several basic channels being utilized can adversely affect the performance of the system (e.g., cause a reduction in the data rate for high speed users).

In the exemplary embodiment, the primary channel for which the shared mode is used by a particular remote station 6 is indicated by an indicator bit sent on the forward control channel. This indicator bit is set for all remote stations 6 in the group when a broadcast message is sent on the shared signaling channel. Otherwise, this indicator bit is set only for the particular remote station 6 that sent the traffic channel frame on the next frame.

VII forward supplemental channel

In an example embodiment, supplemental channels are used to support high speed data services. In an exemplary embodiment, the supplemental channel frame may be transmitted using one of a plurality of data rates, with the data rate used on the supplemental channel being transmitted to receiving remote station 6 via signaling (e.g., forward link scheduling) on a control channel. Thus, the data rate on the supplemental channel need not be dynamically determined by the receiving remote station 6. In the exemplary embodiment, the Walsh codes used for the supplemental channels are communicated to remote station 6 via a logical signaling channel transmitted on the forward fundamental channel.

Forward control channel

In the exemplary embodiment, the control channel is a fixed rate channel associated with each remote station 6. In an example embodiment, the control channel is used to transmit power control information and short control messages for forward and reverse link scheduling (see fig. 3). The scheduling information includes data rates and transmission durations that have been allocated to the forward and reverse supplemental channels.

The use of the fundamental channel may be adjusted by signaling channel frames sent on the control channel. In an example embodiment, the allocation of the logical signaling channel frames is made by an indicator bit within the control channel frame. The procedure basic indicator bit informs the remote station 6 whenever there is information in the next frame directed to the remote station 6 on the basic channel.

The control channel is also used to transmit reverse power control bits. The reverse power control bit instructs remote station 6 to increase or decrease its transmit power in order to maintain a desired level of performance (e.g., as measured by a frame error rate) while minimizing interference to adjacent remote stations 6. Exemplary methods and apparatus for reverse link power control are described in detail in U.S. patent No. 5,056,109, entitled "method and apparatus for controlling transmit power in a CDMA cellular mobile telephone system," which is assigned to the assignee of the present invention and is hereby incorporated by reference. In an example embodiment, the reverse power control bit is transmitted every 1.25 milliseconds on the control channel. To increase capacity and minimize interference, control channel frames are transmitted on the control channel only when there is scheduling or control information available to the remote station 6. Otherwise, the power control bits are sent only on the control channel.

In an example embodiment, the control channel is supported by soft handoff to increase the reliability of reception of the control channel. In an exemplary embodiment, the control channels are placed in and out of soft handoff in a manner specified by the IS-95 standard. In an example embodiment, to expedite the scheduling process for the forward and reverse links, each control frame is one quarter of a traffic channel frame, or 5 milliseconds out of a 20 millisecond traffic channel frame.

IX. control channel frame structure

Example control channel frame formats for forward and reverse link scheduling are shown in tables 1 and 2, respectively. The two separate scheduling control channel frames (one for the forward link and the other for the reverse link) allow for independent forward and reverse link scheduling.

In an example embodiment, the control channel frame format for forward link scheduling includes the type of frame, the assigned forward link rate, and the duration of the forward link rate assignment, as shown in table 1. The type of frame indicates whether the control channel frame is for forward link scheduling, reverse link scheduling, supplemental channel active set, or Erasure Indicator Bits (EIB) and basic frame indicators. Each control channel frame format is discussed below. The forward link rate indicates the data rate allocated for the upcoming data transmission and the duration field indicates the duration of the rate allocation. An example number of bits for each field is shown in table 1, although a different number of bits may be used and is within the scope of the present invention.

TABLE 1

Description of the invention	Number of bits
Type of frame	2
Forward link rate	4
Duration of forward link rate assignment	4
Total up to	10

In an example embodiment, the control channel frame format for reverse link scheduling includes the type of frame, the granted reverse link rate, and the duration of the reverse link rate assignment, as shown in table 2. The reverse link rate indicates the data rate that has been granted for the upcoming data transmission. The duration field indicates the duration of the rate allocation for each carrier.

TABLE 2

Description of the invention	Number of bits
Type of frame	2
Reverse link rate (grant)	4
Duration of reverse link rate assignment	12(4 per carrier)
Total up to	18

In an exemplary embodiment, base station 4 may receive a report from remote station 6 indicating the identity of the strongest pilot in the active set of remote stations 6 and all other pilots in the active set that are received within a predetermined power level (Δ P) of the strongest pilot. This will be discussed in detail below. In response to this power measurement report, base station 4 may send a control channel frame on the control channel to identify a revised set of channels from which remote station 6 will receive supplemental channels. In the exemplary embodiment, the code channels corresponding to the supplemental channels of all members of the existing group are transmitted to remote station 6 via a signaling message.

An example control channel frame format used by the base stations 4 to identify the new set of base stations 4 from which to transmit supplemental channel frames is shown in table 3. In an example embodiment, this control channel frame includes the type of frame and the supplemental current group. In an example embodiment, the supplemental active set field is a bitmap field. In the exemplary embodiment, one of the positions i of this field indicates that the supplemental channel is transmitted from the i-th base station 4 in the existing group.

TABLE 3

Description of the invention	Number of bits
Type of frame	2
Supplement to existing group	6
Total up to	8

An example control channel frame format for the transmit procedure basic channel indication bits and EIBs is shown in table 4. In an example embodiment, this control channel frame includes the type of frame, the fundamental and supplemental channel EIBs, and the process fundamental channel bits. The basic EIB indicates whether a previously received reverse link fundamental channel frame has been deleted. Similarly, the supplemental EIB indicates whether a previously received reverse link supplemental channel frame has been deleted. The process fundamental channel bits (or indicator bits) inform the remote station 6 to demodulate the fundamental channel of information.

TABLE 4

Description of the invention	Number of bits
Type of frame	2
EIB of reverse fundamental channel	1
EIB of reverse supplemental channel	1
Process fundamental channel	1
Total up to	5

X. reverse link channel

In an example embodiment, the reverse link includes the following physical channels: access channels, pilot/control channels, fundamental channels, and supplemental channels. In an example embodiment, the reverse link physical channel facilitates the transmission of various logical channels. The reverse link logical channels include: physical layer control, MAC, user traffic flow, and signaling. A diagram illustrating the relationship between physical and logical channels on the reverse link is shown in fig. 4. The reverse link logical channels are described further below.

XI reverse access channel

In the exemplary embodiment, remote station 6 uses the access channel to send an origination message to base station 4 requesting a fundamental channel. Remote station 6 also responds to the paging message using the access channel. In an example embodiment, the structure of the access channel may be similar to that in an IS-95 system.

Xii reverse fundamental channel

In the exemplary embodiment, voice, data, and signaling messages are transmitted from remote station 6 to base station 4 during communication using a reverse traffic channel. In an example embodiment, the reverse traffic channel includes a fundamental channel and a supplemental channel. The fundamental channel may be used to transmit voice traffic, IS-707 data traffic, and signaling traffic. In the exemplary embodiment, the supplemental channel is used only to transmit high speed data.

In the exemplary embodiment, the frame structure of the reverse fundamental channel IS similar to that in the IS-95 system. Thus, the data rate of the fundamental channel can be dynamically changed and the signal received at the base station 4 can be demodulated using a rate determination mechanism. An exemplary rate determination mechanism is disclosed in pending U.S. patent application No. 08/233, 570 entitled "method and apparatus for determining the data rate of variable rate data transmitted in a communications receiver," filed on 26/4/1994, which is assigned to the assignee of the present invention and is incorporated herein by reference. Another rate determination mechanism is described in U.S. patent application No. 08/730, 863, entitled "method and apparatus for determining the rate of data received in a variable rate communication system," filed on 1996, 10/18, which is assigned to the assignee of the present invention and is incorporated herein by reference. In an exemplary embodiment, signaling information is transmitted over the fundamental channel using the half space burst or space burst format described in the above-mentioned U.S. patent No. 5,504, 773.

Xiii reverse supplemental channel

In an example embodiment, supplemental channels are used to support high speed data services. In an example embodiment, the supplemental channel supports multiple data rates, but this data rate does not change dynamically during transmission. In the exemplary embodiment, remote station 6 requests a data rate on the supplemental channel and is granted permission by base station 4.

XIV. reverse pilot/control channel

In an example embodiment, pilot and control information on the reverse link is time multiplexed on the pilot/control channel. In an example embodiment, the control information includes physical layer control and MAC. In an example embodiment, the physical layer control includes Erasure Indicator Bits (EIB), forward power control bits, inter-cell Δ power levels, and inter-carrier power levels for the forward fundamental and supplemental channels. In an exemplary embodiment, the MAC includes a queue size that represents the amount of information to be transmitted by remote station 6 on the reverse link and the current power headroom (headroom) of remote station 6.

In the exemplary embodiment, two EIB bits are used to support the forward fundamental and supplemental channels. In the exemplary embodiment, each EIB bit indicates an erasure frame that was received two frames ago for the respective forward traffic channel to which the IEB bit was assigned. A discussion of the implementation and use of EIB transmission is disclosed in U.S. patent No. 5,568, 483 entitled "method and apparatus for formatting data for transmission," which is assigned to the assignee of the present invention and is incorporated herein by reference.

In an example embodiment, the forward fundamental and/or supplemental channels may be transmitted from the "best" set of base stations 4. This takes advantage of spatial diversity (diversity) and may result in less power being required for transmission on the forward traffic channel. Remote station 6 transmits the inter-cell Δ power levels on the pilot/control channel to indicate to base station 4 the difference in the power levels received from base station 4 as observed by remote station 6. The base station 4 uses this information to determine the "best" set of base stations 4 to send the forward fundamental and supplemental channels.

In an example embodiment, the inter-cell delta power level is at a highest energy-to-interference ratio (E) per chip (chip)_c／I_o) And in the current group (E thereof)_c／I_oAt the highest E_c／I_oWithin a predetermined power level (Δ P) of pilots) to identify pilots in the active set of remote stations 6. Exemplary methods and apparatus for measuring pilot power levels are disclosed in U.S. patent application No. 08/722, 763, entitled "method and apparatus for measuring link quality in a spread spectrum communication system," filed on 27.9.1996, which is assigned to the assignee of the present invention and is hereby incorporated by reference. In an example embodiment, three bits are used to specify the highest E in the current group_c／I_oOf the pilot (or the specific base station 4). In the exemplary embodiment, the number of pilots in the current group is limited to six. Thus, a bitmap field of length five may be used to identify its E_c／I_oAll pilots within Δ P of the strongest pilot. For example, a "1" may indicate that the pilot assigned to a particular bit position is within Δ P of the strongest pilot and a "0" may indicate that the pilot is not within Δ P of the strongest pilot. Thus, a total of eight bits are used for the inter-cell Δ power level. This is shown in table 3.

TABLE 5

Description of the invention	Number of bits
Basic EIB	1
Supplemental EIB	1
Inter-cell delta power level	8(3+5)
Inter-carrier power level	12(4 bit/carrier wave)
Queue size	4
Power headroom	4

An example of using the inter-cell delta power level to control forward supplemental channel transmission is shown in fig. 5A and 5B. In fig. 5A, initially, base station a transmits the fundamental and supplemental channels, base station B transmits the fundamental channel, and base station C transmits the fundamental channel. Remote station 6 measures the forward link power and determines that the received power level from base station C is higher than the received power level from base station a. Remote station 6 transmits the inter-cell Δ power level to the base station indicating this. Then, as shown in fig. 5B, in response, the forward supplemental channel transmission is handed off from base station a to base station C.

In an example embodiment, the power received on each carrier is reported using an inter-carrier power level. In a multi-carrier environment, different carriers may be individually attenuated (fade), it is possible that one or more carriers experience deep attenuation while the remaining carriers are received significantly more strongly. In an example embodiment, remote station 6 may use the inter-carrier power level to indicate the strength of the carrier.

An exemplary graph of the frequency spectrum of a received multi-carrier signal is shown in fig. 6. Note from fig. 6 that carrier C is received weaker than carriers a and B. In the exemplary embodiment, the three carriers are power controlled together by forward power control bits. The base station 4 may use the inter-carrier power level to assign different rates to each carrier. Alternatively, base station 4 may use the inter-carrier power level from remote station 6 to increase the transmit gain of the weaker carrier to achieve the same energy-per-bit-to-interference ratio E_c／I_oAll carriers are received.

In the exemplary embodiment, up to 16 rates need to be scheduled for the reverse link. Thus, 16 levels of quantization are sufficient to specify the power headroom of remote station 6. The maximum reverse link rate can be expressed as:E_b_Required

here, E_bRequired is the energy per bit Required for the remote station 6 to transmit on the reverse link. From equation (1) and assuming that base station 4 uses 4 bits to indicate the granted Rate, a one-to-one relationship between Max _ Rate _ grant and Power _ Headroom is Possible if 4 bits are allocated to the Power Headroom parameter. In an example embodiment, multiple is supportedUp to three carriers. Thus, this inter-carrier power level includes 12 bits to identify the strength of each of the three carriers (4 bits per carrier).

Once the base station 4 determines the granted rate, the duration of the reverse link rate allocation may be calculated using the queue size information from the remote station 6 by the following relationship: power _ Headroom

Queue_Size=Reverse_Rate·Assignment_Duration (2)

(queue size = reverse rate assignment duration)

Thus, the granularity of the queue size should be the same as the granularity (e.g., 4 bits) used by the base station 4 to specify the duration of the rate allocation.

The above discussion assumes that a maximum of 16 rates and a maximum of three carriers need to be scheduled. Different numbers of bits may be used to support different numbers of carriers and rates and are within the scope of the invention.

XV. timing and scheduling

As described above, the control information is time-multiplexed with the pilot data. In an example embodiment, the control information is spread within one frame so that continuous transmission occurs. In the exemplary embodiment, each frame is further partitioned into four equal control frames. Thus, for a 20 millisecond frame, each control frame is 5 milliseconds in duration. It is contemplated and within the scope of the invention that the forward channel frame may be divided into a different number of control frames.

A diagram of an exemplary reverse link pilot/control channel frame format is shown in fig. 7A. In the exemplary embodiment, inter-cell Δ power level 112 is transmitted in a first control frame of a frame, inter-carrier power level 114 is transmitted in a second control frame, EIB bit 116 is transmitted in a third control frame, and reverse link rate request (RL rate request) 118 is transmitted in a fourth control frame.

An example timing diagram illustrating reverse link high speed data transmission is shown in fig. 7B. In block 212, farStation 6 sends an RL rate request to base station 4 within the fourth control frame of frame i. In an example embodiment, the RL rate request includes a 4-bit queue size and a 4-bit power headroom as described above. In block 214, channel element 42 receives the request in the first control frame of frame i +1 and communicates this request with E required by remote station 6_b／N_oSent together to the scheduler 12. In block 216, the scheduler 12 receives the request in the third control frame of frame i +1 and schedules the request. The scheduler 12 then sends this schedule to the channel element 42 in the first control frame of frame i +2 in block 218. In block 220, channel element 42 receives this schedule within the third control frame of frame i + 2. In block 222, a forward link control frame containing the reverse link schedule is transmitted to remote station 6 within the third control frame of frame i + 2. Remote station 6 receives this reverse link schedule in the fourth control frame of frame i +2 at block 224 and begins transmitting at the scheduled rate in frame i +3 at block 226.

Base station 4 uses the inter-cell Δ power level transmitted by remote station 6 within the first control frame to select base station 4 from which to transmit the supplemental channel. An example timing diagram using inter-cell Δ power levels is shown in fig. 7C. At block 242, remote station 6 transmits the inter-cell Δ power level to base station 4 within the first control frame of frame i. At block 244, channel element 42 receives this inter-cell Δ power level in the second control frame of frame i and sends this information to Base Station Controller (BSC) 10. At block 246, the base station controller 10 receives this information in the fourth control frame of frame i. The base station controller 10 then determines a new set of active supplemental channels in the first control frame of frame i +1 at block 248. At block 250, channel element 42 receives the forward link control channel frame containing the new supplemental existing group at the third control frame of frame i +1 and transmits it on the forward link control channel. At block 252, remote station 6 ends decoding the forward link control channel frame within the fourth control frame of frame i + 1. At block 254, remote station 6 begins demodulation of the new supplemental channel at frame i + 2.

Base station 4 uses the inter-carrier power level transmitted by remote station 6 within the second control frame to allocate a rate to each carrier to support remote station 6. An example timing diagram using inter-carrier power levels is shown in fig. 7D. At block 262, remote station 6 transmits the inter-carrier power level within the second control frame of frame i. At block 264, channel element 42 decodes the frame within the third control frame of frame i. At block 266, the base station 4 receives the inter-carrier power level in the fourth control frame of frame i and allocates a rate to each carrier. In an example embodiment, the inter-carrier power level is not routed over the backhaul (backhaul). Therefore, appropriate operation can be enabled in the next frame after the inter-carrier power level is received. At block 268, a forward link control channel frame containing the rate for each carrier is transmitted within the first control frame of frame i + 1. At block 270, remote station 6 completes decoding the forward link control frame within the second control frame of frame i + 1. At block 272, remote station 6 begins demodulation at the new rate of the carrier within frame i + 2.

In the exemplary embodiment, an EIB bit is transmitted on the pilot/control channel within the third control frame to indicate an erasure frame received by remote station 6 on the fundamental and supplemental channels. In an example embodiment, high speed data traffic may use the EIB bit as a layer 2 Acknowledgement (ACK) or Negative Acknowledgement (NACK) instead of a NACK (negative acknowledgement) Radio Link Protocol (RLP) frame as defined by the IS-707 standard entitled TIA/EIA/IS-707 data traffic options for wideband spread spectrum systems. The EIB bits of this embodiment are shorter and have less processing delay than NACK RLP frames. An example timing diagram for transmitting the EIB bit is shown in fig. 7E. At block 282, remote station 6 receives data on the traffic channel on the forward link in frame i-2. At block 284, the remote station 6 ends decoding frame i-2 in the first control frame of frame i and determines whether to delete the data frame. At block 286, remote station 6 transmits an EIB bit on the forward traffic channel within the third control frame of frame i that represents the status of the data frame received in frame i-2.

The reverse link pilot/control channel frame format described above is an exemplary format that minimizes processing delays using procedures contained within the pilot/control channel frame. For some communication systems, some of the information described above is not applicable and is not needed. For example, a communication system operating on one carrier does not require an inter-carrier power level. For other communication systems, additional information is utilized to implement various system functions. Thus, pilot/control channel frame formats containing different information and utilizing different orderings of such information are contemplated as being within the scope of the present invention.

Xvi. remote station mode of operation

In an exemplary embodiment, to more fully utilize the available forward and reverse link capacity, the traffic channel is dropped during periods of inactivity. In the exemplary embodiment, remote station 6 operates in one of three modes: traffic channel mode, suspended mode, and dormant mode. The transition of each mode depends on the length of the inactive period.

An example timing diagram for transitioning to the suspend and hibernate modes is shown in fig. 8A, and an example state diagram for transitioning between the operating modes is shown in fig. 8B. Traffic (or activity) in the forward and/or reverse traffic channels is represented by remote station 6 being in traffic channel patterns 312a, 312B, and 312c in fig. 8A and traffic channel pattern 312 in fig. 8B. By T_idle(T_{Free up}) The inactive period is shown to be of a duration since the last data transmission was terminated. In an example embodiment, if the off-period exceeds a first predetermined idle period T_sThen remote station 6 is in park mode 314. Once in the pause mode 314, if the inactive period exceeds a second predetermined idle period T_d(Here, T_d＞T_s) Then remote station 6 is in sleep mode 316. In either the suspended mode 314 or the dormant mode 316, if either the base station 4 or the remote station 6 has data to transmit over the communication, a traffic channel is assigned to the remote station 6 and returned to the traffic channel mode 312 (as shown in fig. 8B). In an example embodiment, T is selected_sApproximately one second, select T_dApproximately 60 seconds, although T may be paired_sAnd T_dOther values are selected and are within the scope of the invention.

Xvii. remote station pause mode

Exceeding a first predetermined idle period T during the inactive period_sThe remote station 6 enters a pause mode. In the exemplary embodiment, in the suspended mode, the traffic channel is dropped, but remote station 6 and base station 4 retain state information so that remote station 6 can return to the traffic channel mode for a short period of time. In an example embodiment, the state information stored in the suspended mode includes RLP state, traffic channel configuration, encryption variables, and authentication variables. These state information are defined by the IS-95 and IS-707 standards. The traffic channel configuration may include a traffic configuration, associated traffic options and their characteristics, and power control parameters. Since the state information is stored, remote station 6 may return to the traffic channel mode and be assigned a traffic channel upon receiving the channel assignment message.

In the exemplary embodiment, in the suspended mode, remote stations 6 continuously monitor the paging channel in a non-slotted mode and process overhead messages broadcast on the paging channel to all remote stations 6. The remote station 6 may send a location update message to the base station 4 to inform the base station controller 10 of its current location. An exemplary diagram of a situation where a remote station 6k operating in a suspended mode sends a location update message when a new pilot is detected is shown in fig. 8C. Remote station 6k receives pilots from base stations 4i and 4j and a new pilot from base station 4 k. The remote station 6k then transmits a location update message on the reverse link, which is received by base stations 4i, 4j, and 4 k. Remote station 6k may also send a suspend location update message if the pilot from one of base stations 4 falls below a predetermined threshold. In an example embodiment, the pause location update message is sent on an access channel.

In the exemplary embodiment, the location update message is routed by the base station 4 to the base station controller 10. Thus, base station controller 10 is readily aware of the location of remote station 6 and may compose a channel assignment message and may place remote station 6 into traffic channel mode in soft handoff mode.

Xviii. remote station sleep mode

In an exemplary embodiment, remote station 6 monitors the paging channel in a slotted mode while in sleep mode to conserve battery power. In an exemplary embodiment, the sleep mode IS similar to the mode defined by the IS-707 standard.

In the exemplary embodiment, in the dormant mode, neither base station 4 nor remote station 6 maintains state information relating to the call, and remote station 6 and base station 4 maintain only the point-to-point protocol (PPP) state. As a result, the remote station 6 and base station 4 traverse (reverse through) the call setup procedure (including paging, page response, and channel assignment) before the remote station 6 is assigned a traffic channel and returns to traffic channel mode.

Xix. transition to traffic channel mode

In an example embodiment, the transition of remote station 6 from the suspend or sleep mode to the traffic channel mode may be initiated by either base station 4 or remote station 6. An exemplary diagram of a base station initiated protocol for transitioning from suspend and dormant modes to traffic channel mode is shown in fig. 9A and 9B, respectively. If base station 4 has data to transmit to remote station 6, base station 4 initiates the process. If remote station 6 is in a suspended mode (see fig. 9A), base station 4 transmits a channel assignment message on the paging channel, after which data transmission may occur shortly. If remote station 6 is in sleep mode (see fig. 9B), base station 4 first transmits a paging message on the paging channel. Remote station 6 receives the page message and sends a page response message upon acknowledgement. The base station 4 then transmits a channel assignment message. After a series of service negotiation messages, call setup is completed and data transmission occurs thereafter. As shown in fig. 9A and 9B, the transition from the suspend mode to the traffic channel mode is faster than the transition from the sleep mode to the traffic channel mode because the remote station 6 and the base station 4 maintain the state of the call.

Exemplary diagrams of protocols for remote station initiated transitions from suspend and dormant modes to traffic channel mode are shown in fig. 9C and 9D, respectively. Remote station 6 initiates this process if remote station 6 has data to transmit to base station 4. If remote station 6 is in the suspended mode (see fig. 9C), remote station 6 sends a reconnect message to base station 4. The base station 4 then transmits a channel assignment message, after which data transmission can occur very quickly. If remote station 6 is in sleep mode (see fig. 9D), remote station 6 first sends an origination message to base station 4. The base station 4 then transmits a channel assignment message. After a series of service negotiation messages, call setup is complete, after which data transmission may occur.

The present invention has been described in terms of a number of physical channels that facilitate communication of the aforementioned plurality of logical channels. Other physical channels may also be utilized to implement additional functionality that may be required by a communication system using these channels. Further, the above-described physical channels may be multiplexed and/or combined so that the desired functions may be accomplished, and various combinations of physical channels are within the scope of the present invention.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (41)

1. A channel structure for a communication system, characterized by:

at least one fundamental channel for transmitting traffic data, voice data, and signaling;

a supplemental channel for transmitting traffic data; and

a paging channel for transmitting paging messages.

2. The channel structure of claim 1 wherein said fundamental channel is supported by soft handoff.

3. The channel structure of claim 1 wherein said fundamental channel is allocated for the duration of a communication.

4. A channel structure as claimed in claim 3, wherein a remote station drops said fundamental channel if the period of inactivity of said remote station exceeds a first predetermined threshold.

5. The channel structure of claim 4 wherein said state of communication is maintained if said period of inactivity of said remote station exceeds said first predetermined threshold.

6. The channel structure of claim 5 wherein said state of said communication is not maintained if said period of inactivity of said remote station exceeds a second predetermined threshold.

7. The channel structure of claim 1 wherein said supplemental channel is allocated to a remote station for high speed data transmission.

8. The channel structure of claim 1 wherein said supplemental channel is capable of data transmission at one of a plurality of data rates.

9. The channel structure of claim 1 wherein said supplemental channel is not supported by soft handoff.

10. The channel structure of claim 1 wherein said supplemental channel is transmitted from a best base station in an active set of remote stations.

11. The channel structure of claim 1 wherein said supplemental channel is transmitted at a fixed data rate for the duration of the transmission.

12. The channel structure of claim 11 wherein said fixed data rate is allocated in accordance with the amount of data to be transmitted.

13. The channel structure of claim 11 wherein said fixed data rate is allocated in accordance with a power headroom of a transmitting source.

14. The channel structure of claim 11 wherein said fixed data rate is allocated in accordance with energy per bit required for said transmission.

15. The channel structure of claim 1 wherein said fundamental channel and said supplemental channel are capable of being transmitted simultaneously.

16. The channel structure of claim 1, further comprising:

a pilot/control channel for transmitting pilot and control messages.

17. The channel structure of claim 16 wherein said control messages are sent on control frames, each of said control frames being part of a traffic channel frame.

18. The channel structure of claim 16 wherein said control message comprises a reverse link data request.

19. The channel structure of claim 18 wherein said reverse link data request includes an indication of an amount of data to be transmitted.

20. The channel structure of claim 18 wherein said reverse link data request includes an indication of power headroom.

21. The channel structure of claim 16 wherein said control message includes a multi-cell delta power level indicative of the power level of pilots received in an active set of remote stations.

22. The channel structure of claim 16 wherein said control message includes a multi-carrier power level indicative of the power levels of the carriers received in the active set of remote stations.

23. The channel structure of claim 16 wherein said control message includes erasure indicator bits indicating an erasure status of a previously received data frame.

24. The channel structure of claim 21 wherein said supplemental channel is transmitted from a base station selected based on said multi-cell Δ power levels.

25. The channel structure of claim 21 wherein said multi-cell Δ power level is transmitted in a first control frame of a traffic channel frame.

26. The channel structure of claim 22 wherein said multi-carrier power level is transmitted within a second control frame of a traffic channel frame.

27. The channel structure of claim 23 wherein said erasure indicator bits are transmitted within a third control frame of a traffic channel frame.

28. The channel structure of claim 18 wherein said reverse link data request is transmitted in a fourth control frame of a traffic channel frame.

29. The channel structure of claim 1, further comprising:

a control channel for transmitting scheduling information and signaling.

30. The channel structure of claim 29, wherein said scheduling information includes an assigned data rate.

31. The channel structure of claim 29, wherein the scheduling information includes a duration of the assigned transmission.

32. The channel structure of claim 29 wherein said signaling includes erasure indicator bits indicating an erasure status of a previously received data frame.

33. The channel structure of claim 29 wherein said signaling information includes an indicator bit indicating whether a message is present on said fundamental channel of a remote station.

34. The channel structure of claim 1 wherein a remote station receives said paging channel in a non-slotted mode if a period of inactivity of said remote station exceeds a first predetermined threshold.

35. The channel structure of claim 1 wherein a remote station receives said paging channel in a slotted mode if a period of inactivity of said remote station exceeds a second predetermined threshold.

36. The channel structure of claim 1, further comprising:

a pilot channel for transmitting pilots.

37. The channel structure of claim 1, further comprising:

a synchronization channel for transmitting system timing information.

38. The channel structure of claim 1, further comprising:

an access channel for sending origination messages and page response messages.

39. A transmitting apparatus for use in a communication system, the apparatus comprising a transmitter for:

transmitting traffic data, voice data and signaling in at least one fundamental channel;

transmitting traffic data in a supplemental channel; and

the paging message is sent in a paging channel.

40. A receiving apparatus for use in a communication system, the apparatus comprising a receiver configured to:

receiving traffic data, voice data and signaling transmitted in at least one fundamental channel;

receiving traffic data transmitted in a supplemental channel; and

a paging message transmitted in a paging channel is received.

41. A communication system comprising two sets of physical channels, one set for a forward link and the other set for a reverse link, the communication system utilizing the physical channels to facilitate communication of logical channels.