HK1153865B - Method, base station and mobile station for tdd operation in a communication system - Google Patents

Description

Method, base station and mobile station for time division duplex operation in a communication system

The present application is a divisional application of the inventive patent application having application number 200480004011.1, filing date 2/11/2004 entitled "method, base station and mobile station for time division duplex operation in a communication system".

Technical Field

The present invention relates to Time Division Duplex (TDD) operation in a communication system, in particular a cellular communication system.

Background

In the field of the present invention, it is well known that both first and second generation cellular communication standards use Frequency Division Duplex (FDD), where there are separate downlink (base station to mobile station) and uplink (mobile station to base station) frequency allocations. These allocations are separated by a "duplex gap" to avoid interference between simultaneous transmissions and receptions by the base station and the mobile station. FDD allocations are typically referred to as "paired spectrum".

Time Division Duplexing (TDD) is used in more recent standards, such as "third generation partnership project" (3GPP) "time division-code division multiple access" (TD-CDMA) and 3GPP "time division-synchronous code division multiple access" (TD-SCDMA). In a TDD system, transmission and reception occur on the same frequency in a time alternating manner. TDD is well suited for packet data communications where the capacity of the uplink and downlink can be easily adjusted to meet the traffic distribution of the users.

TDD is not used in FDD bands due to interference concerns. TDD can operate in the mobile transmit (uplink) portion of the FDD band without harmful interference. The allocation of TDD channels next to FDD uplink channels in the "international mobile telecommunications 2000" (IMT-2000, the "3G" frequency band specified by the international telecommunications union) provides proof of the feasibility of this aspect. The frequency allocation of IMT-2000 is shown in FIG. 1.

However, operating TDD in the downlink portion of the FDD band is problematic due to adjacent channel interference from existing FDD base stations to receivers of co-located or adjacent TDD base stations, both of which typically transmit higher power than the corresponding user terminals.

Thus, when a wireless operator has an FDD spectrum allocation, TDD techniques can typically only operate on the FDD uplink portion of the spectrum, leaving the FDD downlink spectrum unutilized and effectively "wasted".

There is therefore a need for a design arrangement, method and unit for TDD operation in a communication system that alleviates the above disadvantages.

Disclosure of Invention

According to a first aspect of the present invention there is provided a base station for communicating with user equipment in a communication system, wherein the base station comprises a lower downlink frequency carrier element and an upper downlink frequency carrier element, and wherein the base station is operable to communicate with the user equipment using both lower and upper downlink carrier frequencies.

According to a second aspect of the present invention, there is provided a method of communicating between a base station and a user equipment in a communication system, comprising: communication is simultaneously sent from the base station to the user equipment in the lower and upper frequency bands.

According to a third aspect of the present invention there is provided a user equipment for communicating with a base station in a communication system, wherein the user equipment comprises a lower downlink frequency carrier element and an upper downlink frequency carrier element, and wherein the user equipment is operable to communicate with the base station using both lower and upper downlink carrier frequencies.

Drawings

A method, a base station and a mobile station for TDD operation in a communication system employing the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic block diagram of an IMT-2000 frequency allocation;

fig. 2 shows a schematic block diagram of TDD with auxiliary downlink utilization; and

fig. 3 shows a schematic block diagram of the system architecture for TDD with auxiliary downlink.

Detailed Description

The invention is based on the realization of the inventor, and can:

operation of the TDD technique is implemented in one frequency band allocated as a pair of frequency spectra for FDD.

Provide the ability to efficiently use the FDD downlink spectrum to provide capacity, thereby avoiding waste. This is called the auxiliary TDD downlink channel.

Avoiding harmful interference in TDD operation in FDD downlink spectrum.

Remove the fixed duplex frequency separation requirement.

An example of TDD operation with auxiliary downlink is shown in fig. 2. As shown, standard TDD operates in the uplink FDD spectrum (210), while the secondary downlink operates in the downlink FDD spectrum (220). In the figure, a frame structure having 15 slots is shown. An upward pointing arrow in a radio frame represents an uplink time slot and a downward pointing arrow represents a downlink time slot. As can be seen, by using the auxiliary downlink, the system capacity is enlarged.

Fig. 3 shows the basic architecture of a third generation partnership project (3GPP) cellular communication system 300 employing the present invention. As shown, a node B (or base station) 320 is controlled by a Radio Network Controller (RNC)310 (over the "Iub" interface) and communicates with user equipment (UE or mobile terminal) 330 over the Uu radio interface.

It will be understood that, in other aspects, system 300 will operate in accordance with relevant 3GPP technical specifications (available from the website http:// www.3gpp.org.), and need not be described in further detail herein. However, as will be explained further below, for node B320, it is noted that the base station (node B) includes a lower band logical unit 322 and an upper band logical unit 324 which operate simultaneously in the upper (FDD downlink) and lower (FDD uplink) frequency bands under the control of RNC 310.

The lower band logic unit 322 supports normal TDD operation, where the radio resources are divided into individual time slots.

The higher band logic unit 324 supports secondary downlink operation. This logic unit supports only downlink operation. The radio resources are divided into individual time slots.

In the system of fig. 3, 3 types of UEs 330 may be supported:

1. single frequency standard TDDUE (not shown):

this is a standard tdd ue, where both the uplink and downlink operate on a single frequency. This type of UE will operate by communicating with the lower band logical unit in the node B.

2. Single instantaneous frequency UE (not shown):

this type of UE can tune to two different frequencies (lower and upper FDD bands) in the same TDD frame under control of the network. The UE operates uplink transmission in the lower FDD band. Under control of the network, the UE may operate in either a standard TDD downlink (lower FDD band) or an auxiliary downlink (upper FDD band).

3. Dual simultaneous frequency UE 330:

this type of UE has a lower band uplink/downlink (UL/DL) logic 322, a higher band "auxiliary downlink" logic 324, and an "auxiliary downlink" capability messaging logic 336, and is capable of tuning to both the lower and upper FDD bands. The UE operates uplink transmission in the lower FDD band. The UE operates a standard TDD downlink (lower FDD band) and an auxiliary downlink (upper FDD band) under control of the network. With dual simultaneous frequency capability, the UE can operate with increased downlink capacity.

In the operation of the system of fig. 3, the auxiliary downlink ("AuxDL") capability allows the inherent TDD technology to efficiently utilize the FDD downlink band, avoiding waste of spectrum, and the downlink resources in the lower and upper bands are treated as a combined "single pool" of resources that can be allocated to users as needed. Node B320 provides common signaling for both FDD frequencies.

At any time, individual UEs that can support the "auxiliary downlink" mode of operation may be allocated downlink capacity in the lower frequency band or the higher frequency band or both.

UEs and node bs exchange "auxiliary downlink" capability messages so that UEs and node bs with and without the "auxiliary downlink" feature can coexist in the network and each operate in a manner that best performs their respective capabilities.

UEs that do not support auxiliary downlink, e.g., roaming UEs from another TDD network, may be compatible with the auxiliary downlink architecture by operating in a standard TDD mode in the lower frequency band. In this case, the secondary downlink feature is transparent to the UE.

While the auxiliary downlink increases the total downlink capacity, it also increases the uplink capacity since additional time slots in the lower TDD band can be allocated to uplink traffic channels.

The separation of the lower and upper frequency bands is not limited by the standard FDD duplex frequency separation. Instructing, by the network, the UE to tune to the correct frequency for the auxiliary downlink. At the network level, the auxiliary downlink at the higher frequency band may even be adjacent to the lower frequency band (even if the UE is required to operate only on one downlink frequency at a time in order to minimize the receive filtering requirements). This effectively allows operators to use the proposed TDD technology in adjacent frequency allocations.

It will be appreciated that the above-described design arrangements, methods and elements for TDD operation in a communication system will provide the following benefits:

provide a flexible approach to using time division duplex architecture in frequency division duplex spectrum.

By adjusting the capacity split of the uplink and downlink, flexible use of system capacity is allowed.

Remove previous FDD duplex restrictions.

Claims (16)

1. A base station for communicating with a user equipment in a communication system, wherein the base station comprises lower band logic units and higher band logic units, and wherein the base station is operable to communicate with the user equipment using a first frequency band and a second frequency band simultaneously,

wherein the lower band logical unit is arranged to operate in TDD uplink and downlink mode in a first frequency band allocated for FDD uplink communication; and

the higher frequency band logical unit is configured to operate in a TDD downlink mode only in a second frequency band allocated for FDD downlink communication.

2. The base station of claim 1, further comprising: means for using common signaling for the first frequency band and the second frequency band.

3. The base station of claim 1 or 2, further comprising: means for exchanging messages with user equipment of the system to determine whether the user equipment is capable of operating in TDD mode in a frequency band allocated for operation in FDD mode, and communicating with the user equipment accordingly.

4. The base station of claim 1 or 2, further comprising: means for managing a plurality of frequencies as a single resource.

5. The base station of claim 1 or 2, wherein the lower band logical unit comprises: means for increasing uplink capacity by increasing allocation of uplink timeslots in the first frequency band.

6. The base station of claim 1 or 2, wherein the system comprises a third generation partnership project, 3GPP, system and the base station comprises a node B.

7. A method of communicating between a base station and user equipment in a communication system, comprising:

sending out communication from the base station to the user equipment in a first frequency band and a second frequency band simultaneously in a downlink,

wherein said simultaneously issuing communications from the base station to the user equipment in a first frequency band and a second frequency band comprises:

operating in TDD uplink and downlink modes in a first frequency band allocated for FDD uplink communications; and

operating in a TDD downlink mode only in a second frequency band allocated for FDD downlink communication.

8. The method of claim 7, further comprising using common signaling for the first frequency band and the second frequency band.

9. The method of claim 7 or 8, further comprising:

exchanging messages between the base station and the user equipment to determine whether the user equipment is capable of operating in TDD mode in a frequency band allocated for FDD mode, and communicating between the base station and the user equipment accordingly.

10. The method of claim 7 or 8, further comprising:

managing multiple frequencies as a single resource.

11. The method of claim 7 or 8, further comprising increasing uplink capacity by increasing allocation of uplink timeslots in the first frequency band.

12. A user equipment for communicating with a base station in a communication system, wherein the user equipment comprises lower band logic units and higher band logic units, and wherein the user equipment is operable to communicate with the base station in downlink using first and second frequency bands simultaneously,

wherein the lower band logical unit is arranged to operate in TDD uplink and downlink mode in a first frequency band allocated for FDD uplink communication; and

the higher frequency band logical unit is configured to operate in a TDD downlink mode only in a second frequency band allocated for FDD downlink communication.

13. The user equipment of claim 12, further comprising means for using common signaling for the first frequency band and the second frequency band.

14. The user equipment of claim 12, further comprising means for exchanging messages with the base station to determine whether the user equipment is capable of operating in TDD mode in a frequency band allocated for FDD mode operation, and communicating with the base station accordingly.

15. The user equipment of claim 12, wherein the lower band logic unit comprises: means for increasing uplink capacity by increasing allocation of uplink timeslots in the first frequency band.

16. The user equipment of claim 12, wherein the communication system comprises a third generation partnership project 3GPP communication system.