MXPA00005848A - System for transporting frequency hopping signals - Google Patents

Abstract

A system for transporting radio frequency (RF) signals across an RF network comprises a central transport unit (30) and a remote transport unit (50). The frequencies of at least some of the RF signals to be transported may hop in accordance with predetermined hopping sequences. The central transport unit (30) uses the hopping sequences to convert the hopping frequencies into fixed frequencies for efficient transport through the RF network. The remote transport unit (50) uses the hopping sequences to convert the fixedfrequencies back to the original hopping frequencies. The transport system is also capable of reverse operation in the direction from the remote transport unit (50) to the central transport unit (30).

Description

SYSTEM FOR TRANSPORT OF FREQUENCY JUMP SIGNALS BACKGROUND OF THE INVENTION Technical Field The present invention relates to radio frequency (RF) transport systems and more specifically to an RF transport system capable of efficiently transporting RF signals from one or more RF transceivers that use frequency hopping. Previous Related Technology Wireless communications services using RF signals were easily accessible to the general public with the emergence of cellular radio systems. In a typical cellular RF system, a geographic area (eg, a metropolitan area) is divided into several smaller contiguous radio coverage areas, referred to as "cells" that are served by a corresponding group of fixed radio stations called "base stations". ", each of which includes a plurality of radio frequency (RF) channel units (transceivers) operating in a subset of RF channels assigned to the system, as is well known in the art. The RF channels allocated to any given cell can be re-assigned to a distant cell according to a frequency re-use plan as is also well known in the art. In each cell, at least one RF channel called the "control" or "radio location / access" channel is used to carry control or monitoring messages. The other RF channels are used to carry voice conversations and are thus referred to as the "voice" or "speech" channels. Cell phone users (mobile subscribers) in the aforementioned system are usually provided with portable telephone units (manuals), transportable (transported by hand) or mobile (assembled in a car), collectively referred to as "mobile stations", each of which communicates with a nearby base station. Each of the mobile stations includes a microphone, a speaker, a controller (microprocessor) and a transceiver, as is well known in the art. The transceiver in each mobile station can tune to any RF channels specified in the system (while each of the transceivers in the base stations usually operates in only one of the different RF channels employed in the corresponding cell). The base stations in the aforementioned system are connected to and controlled by a Mobile Telephone Switching Office (MTSO) which in turn is connected to a local exchange in the public switched telephone network (PSTN = Public Switched Telephone Network) landline (wired line), or a similar facility such as an integrated service digital network (ISDN = Integrated Services Digital Network). The MTSO switches calls between wired and mobile line subscribers, controlling signals and allocation of voice channels to mobile stations, makes "transfers" of calls from one base station to another, compiles billing statistics, stores profiles of subscriber services and allows the operation, maintenance and testing of the system. The original cellular radio system, as described generally above, employs analog transmission methods, specifically frequency modulation (FM) and duplex RF channels (two-way) in accordance with the Advanced Mobile Telephony Service standard (AMPS = Advanced Mobile Phone Service). In the U.S. , this original AMPS (analog) architecture forms the basis for an industrial standard sponsored by the Electronic Industries Association (EIA = Electronic Industries Association) and the Telecommunications Industry Association (TIA = Telecommunications Industries Association) and known as EIA / TIA- 553. from the middle to the end of the 1980s, however the cell phone industry both in the U.S. as in other parts of the world it started to migrate from analog to digital technology, motivated in large part by the need to address the continued growth in subscriber populations and the increased demand on systems capacity. The industry thus developed a number of air interface standards that use digital voice coding (analog-to-digital conversion and speech compression) and advanced digital radio techniques, such as multiple access time condition (TDMA = Time Division). Multiple Access) or multiple access with code division (CDMA = Code Division Multiple Access), to multiply the number of voice circuits (conversations) per RF channel (ie increase capacity). In Europe and Japan, the GSM and PDC standards, respectively both of which use TDMA have been widely implemented. In the USA, the EIA / TIA has developed a number of digital standards, including IS-54 (TDMA), both of which are "dual mode" standards, since they support the use of original AMPS analog voice channels (AVCHs) and analog control channel (ACCH = Analog Control CHannel), plus more recent digital traffic channels (DTCHs) defined within the existing AMPS structure, in order to facilitate the transition from analog to digital and allow the continuous use of existing analog mobile stations . The dual-mode IS-54 standard, in particular, has become known as the digital AMPS standard (D-AMPS). More recently, EITA / TIA has developed a new specification for D-AMPS, which includes a digital control channel (DTCH = Digital Control CHannel) suitable to support various data services, sometimes referred to as "personal communications services" (PCS). = Personal Communications Services), and extended mobile station battery life. This new specification, which is developed in the IS-54B standard, is the current revision of IS-54 (known as IS-136). Along with the emergence of digital cellular and PCS, there has been a trend towards the integration of telephone and data services with television (TV) networks, computer networks and / or multimedia. Figure 1 shows a typical RF transport system (inside the dotted box) that interconnects a cellular or radio base station PCS (RBS = Radio Base Station) 10 with a mobile station (MS) 20. The transport system of RF, comprises a central transport unit 12, an RF transport network 14 and a remote transport unit 16. The central transport unit 12 receives an RF signal at a first frequency fx suitable for transmission over a transport network of RF 14. Depending on the application, the RF transport network 14 may comprise, for example, a local area network (LAN = Local area Network), a wide area network (WAN = Wide area Network), the global communications network known as the Internet, a wired or "wireless" cable TV network, a video network, a fiber optic network, or a point-to-point microwave network. The signal that is transported through the RF transport network 14 at the frequency fy is finally provided to the remote transport unit 16 which converts this signal into a signal at a third frequency fz for transmission through an antenna 18 to MS 20. The use of RF transport systems as generally illustrated in Figure 1, is complicated in practice by the use of frequency "hopping" at the base station. Some cellular and PCS systems, such as those that implement the GSM standard, vary (jump) the frequency of the signal transmitted from the base station to the mobile station over time, in order to reduce the deteriorating effects of Rayleigh fading (the phenomenon wherein the received signal strength will vary due to propagation of multiple paths of the transmitted signal). By rapidly changing the frequency of the signal transmitted from the base station, the fading locations will vary with the course of a call, thereby decreasing the average depth and duration of fade subsidence in the mobile station. Of course, the receiver in the mobile station must jump along with the transmitter in order to receive the signal correctly. For this purpose, the synchronization information with respect to the relevant jump sequence is usually transmitted from the base station to the mobile station on a dedicated or broadly distributed control channel. Figure 2 illustrates the use of frequency hopping in the RBS 10 that is illustrated in Figure 1. The RBS 10 includes a plurality of transceivers 11 such as transceivers 1 ... 5. One of the transceivers (for example transceiver 1) in the RBS 10, is used for control channel signaling and is assigned a frequency f? . Each of the other transceivers (eg transceivers 2 ... 5) in the RBS 10, on the other hand, jumps with a pre-defined set of frequencies such as F2-f5 using a single hop sequence that defines the order of frequencies in its output over time. For example, in a TDMA system where the jump sequence is repeated every four bursts, the outputs of the frequency hopping transceivers (transceivers 2 ... 5) can be as illustrated in Figure 3. Alternately, it is possible to assign each of the transceivers 2 ... 5 to a fixed frequency in the set f2-f5 and to generate the outputs shown in Figure 3, by switching each power signal between those transceivers according to the jump sequence as described in WO 92/09154. When transmitting the various outputs of the frequency hopping transceivers (transceivers 2 ... 5) through the RF transport network 14, it is convenient that the various output frequency signals are "packed" together in order of making efficient use of the available bandwidth in the network 14, and that the packed signals are translated into signals in some predefined area of the spectrum, in such a way that they can co-exist with other RF signals (for example TV signals by cable or satellite), which are transmitted simultaneously on the network 14. Upon leaving the RF transport system, these signals, packaged and translated, can be "unpacked" and translated back to their original frequencies for transmission through the antenna 18 to MS 20. Current implementations of RF transport systems, however, do not allow this desired packing of the jump frequencies. On the contrary, these systems employ the so-called "block conversion", where a block of frequencies from another sector becomes an equal block of frequencies in a different part of the spectrum that is suitable for transmission over the network. , without any frequency packaging. This approach clearly wastes valuable bandwidth in the transport network. COMPENDIUM OF THE INVENTION The present invention seeks to overcome the disadvantages of existing RF transport systems, by recognizing that if the jump frequencies used by the transceivers 2 ... 5 in the base station 10 (which is external to the transport system RF) are made known to the RF transport system, will be able to pack the hopping frequencies in the central transport unit and unpack them in the remote transport unit in a way that achieves or achieves bandwidth efficiency gains wanted . In one aspect, the present invention provides a radio frequency (RF) transport system including a central transport unit, and a remote transport unit, for efficiently transporting through a transport network a plurality of RF signals transmitted from a central station (e.g. a radio base station) at least to a remote station (e.g., a mobile station). The frequency of each of the RF signals may jump according to a pre-determined jump sequence, which is also transmitted from the central station to each remote station (for example on a control channel from the base station to the station). mobile) . The central transport unit includes means for receiving the frequency hopping signals and the jumping sequences from the central station, means for respectively converting central station signals into central unit signals; and means for transmitting the central unit signals and the jumping sequences through the transport network. The remote transport unit includes means for receiving the central unit signals and the jump sequences from the central transport unit; means for respectively converting the central unit signals into remote unit signals; and means for transmitting remote unit signals and hop sequences at least to a remote station. The central transport unit of the present invention further includes means for decoding the jump sequences that are received from the central station; and means for distributing the decoded jump sequences to the means for frequency conversion in the central transport unit, such that the frequency hopping signals of the central station can be respectively converted into the fixed frequency signals of the central unit which can pack efficiently within a predetermined bandwidth before transmitting to the remote transport unit. The remote transport unit of the present invention further includes means for decoding the jump sequences that are received from the central transport unit; and means for distributing the decoded jump sequences to the frequency conversion means in the remote transport unit, such that the fixed frequency signals of the packed central unit can be unpacked and converted to remote unit frequency hopping signals corresponding to the signals of the central station, before transmitting to the remote station at least. The RF transport system of the present invention is also capable of efficiently transporting RF signals from the remote station to the central station. Accordingly, the frequency conversion means in the remote transport unit can respectively convert frequency hopping signals from the remote station at least to fixed frequency signals of the remote unit, which are efficiently packaged within a width of Default band for transmission to the central transport unit. In addition, the frequency conversion means in the central transport unit can respectively convert the fixed frequency signals of the remote unit into respective central unit frequency hopping signals corresponding to the remote station signals for transmission to the central station . These and other aspects of the present invention will be readily available from the detailed description taken in conjunction with the drawings as set forth below. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood than its numerous objects and advantages will be apparent to those skilled in the art by reference to the following drawings wherein: Figure 1 is a block diagram of a radio transport system exemplary frequency (RF) that interconnects a radio base station with a mobile station; Figure 2 is an illustration of the RF transport system of Figure 1, where frequency "hopping" is used by a number of transceivers in the base station, - Figure 3 shows an exemplary frequency hopping sequence to the output of each of the frequency hopping transceivers in the base station in Figure 2; Figure 4 shows the Joase station of Figure 2 interconnected with an RF transport system constructed in accordance with the present invention; and Figure 5 shows an exemplary mapping of the output of each of the frequency hopping transceivers in the base station of Figure 2 at a desired fixed frequency in the RF transport system of Figure 4. DETAILED DESCRIPTION OF THE INVENTION Now with reference to Figure 4, an RF transport system constructed in accordance with the present invention comprises a central transport unit 30 communicating with the RBS 10, and a remote transport unit 50 communicating with the MS 20. The central transport unit 30 includes a plurality of frequency conversion units 32 (units 1 ... 5) for converting the respective outputs of the transceivers 11 (transceivers 1 ... 5) into frequencies that are compatible with the transmission network. transport. In accordance with the present invention, the frequency conversion units 32 are capable of converting both the jump and fixed frequency signals from the transceivers 11 into constant frequency signals that can be efently packaged together for transport through the network. For this purpose the system of the present invention detects the jump sequences employed by the jump transceivers of frequency 2 ... 5 and provides those sequences to the corresponding frequency conversion units 2 ... 5, which are then capable of perform the necessary conversion from the jump frequencies to fixed frequencies. As mentioned above, the information regarding the jump sequences used by the transceivers 2 ... 5, respectively, is transmitted over the control channel that is supported by the transceiver 1 in the RBS 10. As illustrated in Figure 4 , the central transport unit 30 of the present invention includes a combination of demodulator and decoder 34 to demodulate and decode the control channel signal from the transceiver 1, and a jump sequence extraction and distribution unit 36, to extract the information regarding the jump sequence used by each of the transceivers 2 ... 5 and to distribute the information to the appropriate frequency conversion units 2 ... 5. As illustrated in Figures 4-5, the frequency conversion units 32 convert the outputs of the transceivers 11 into constant frequencies fa ... fb, respectively, that are "packed" (ie adjacent to each other) within the spectrum used by the transport network.

As will be appreciated by persons of ordinary skill in the art, each of the frequency conversion units 32 may be constituted by a programmable frequency synthesizer, to generate a reference signal, and a mixer to combine the reference signals with the power frequency jump signal, to generate the desired fixed frequency signals. During operation, the frequency of the reference signal of each of the frequency conversion units 2 ... 5 can be programmed dynamically, based on the corresponding jump sequence information so that the output signal remains at a constant frequency. For example, with reference to Figures 3-5, during burst 1, the frequency of the output of transceiver 2 is f2 and the frequency of the reference signal of frequency conversion unit 2 can be adjusted to (fb-f2 ). The mixer will then generate the desired output frequency in fb. Similarly, during the burst 2, the frequency at the output of the transceiver 2 f4 and the frequency of the reference signal in the frequency conversion unit 2 can be set to (fb-f4), in order to generate again the frequency of desired output fb. It will be noted that the reference signal in the frequency conversion unit I can be set to (fb-fx), for all bursts since the frequency of the output of the transceiver 1 is fixed to fx. Since the remote transport unit 50 must be capable of "unpacking" and reconverting the outputs of the frequency conversion units 32 to their original form of transmission to the MS 20 (and similar mobile stations), the jump sequence information is provided to a combination of encoder and modulator 38 and combined with the outputs of the frequency conversion units 32 in a combiner 40 for transmission through the transport network to the remote transport unit 50 In the remote transport unit 50, the received signals are first separated in a separator 52 and the fixed frequency signals are fed to a plurality of frequency conversion units 54 (units 1 ... 5) which are structurally similar to the frequency conversion units 32. The received hop sequence information is processed through a demodulator and decoder 56 and then fed to the high sequence distribution and extraction unit 58 that distributes the information to the conversion units of Appropriate frequency 2 ... 5. Once the received signals have been reconverted to their original frequencies in the frequency conversion units 54, they are combined in a combiner 60 and transmitted through the antenna 18 to the MS 20 (and similar mobile stations). It will be noted that the operation of the present invention in the reverse direction from the MS 20 to the BS 10 is essentially an image in the mirror of the operation in the forward direction as described above. In other words, the remote transport unit 50 will use the jump sequence information that is received from the central transport unit 30 to convert the hop frequency signals from the MS 20 (and similar mobile stations) into a frequency signal. fixed that is transmitted to the central transport unit 30 to be reconverted back to its original hop frequency (based on the same jump sequence information) before transmission to the BS 10. In this way, the transport system of the present invention is transparent to both BS 10 and MS 20 which continues to transmit and receive frequency hop signals as usual. While certain forms or embodiments of the present invention have been illustrated and described above, those skilled in the art will readily recognize that many modifications and variations may be practiced to or substituted in those formats or embodiments without departing substantially from the scope of the present invention. Accordingly, the forms or embodiments of the present invention described herein are exemplary and are not intended as limiting the scope of the present invention as defined in the following claims.

Claims (20)

1. - A radio frequency (RF) transport system, for transporting through a transport network a plurality of RF signals transmitted from a central station to at least one remote station, the frequency of each of the RF signals jumps according to a predetermined skip sequence which is also transmitted from the central station to the remote station, the transport system comprises a central transport unit and a remote transport unit, the central transport unit includes means for receiving the signals of frequency hopping and jump sequences from the central station, means for respectively converting the central station signals into central unit signals; and means for transmitting the central unit signals and the jumping sequences through the transport network by the remote transport unit, including means for receiving the signals of the central unit and the jump sequences from the central transport unit; means for respectively converting the central unit signals into remote unit signals; and means for transmitting the remote unit signals and the jump sequences to at least one remote station, wherein: the central transport unit further includes means for decoding the jump sequences that are received from the central station; and means for distributing the decoded jump sequences to the frequency conversion means in the central transport unit, such that the frequency hopping signals of the central station can be respectively converted into fixed frequency signals of the central unit, which they can be efficiently packaged within a predetermined bandwidth before being transmitted to the remote transport unit; and the remote transport unit further includes means for decoding the hop sequences that are received from the central transport unit; and means for distributing the decoded jump sequences to the frequency conversion means in the remote transport unit, such that the fixed frequency signals of the packed central unit can be unpacked and converted into remote unit frequency hopping signals , which correspond to the signals of the central station before transmitting to the remote station at least.

2. - The system according to claim 1, characterized in that the network comprises the Internet.

3. - The system according to claim 1, characterized in that the network comprises a local area network (LAN = Local area Network).

4. - The system according to claim 1, characterized in that the network comprises a wide area network (WAN = Wide Area Network).

5. The system according to claim 1, characterized in that the network comprises a wired or wireless cable TV network.

6. - The system according to claim 1, characterized in that the network comprises a video network.

7. The system according to claim 1, characterized in that the network comprises a network of optical fibers.

8. The system according to claim 1, characterized in that the network comprises a point-to-point microwave network.

9. - The system according to claim 1, characterized in that the frequency conversion means in the remote transport unit also respectively convert the frequency hopping signals from the remote station to at least fixed-frequency signals of the remote unit respectively, which can be efficiently packaged within a predetermined bandwidth for transmission to the central transport unit; and the frequency conversion means in the central transport unit also respectively convert the fixed unit frequency signals of the remote unit into center unit frequency hopping signals corresponding to the remote station signals for transmission to the central station. -

10. - The system according to claim 9, characterized in that the central station comprises a radio base station, the remote station comprises a mobile station and the jump sequences are transmitted from the base station to the mobile station on a control channel.

11. Method for transporting a plurality of radio frequency (RF) signals from a central station to a plurality of remote stations through a transport network between a central transport unit and a remote transport unit, the frequency of each one of the RF signals jumps according to the predetermined jump sequence that is sent from the central station to each of the remote stations, the central transport unit receives and respectively converts the central station signals into central unit signals for transmission through the transport network, and the remote transport unit receives and converts respectively the central unit signals into remote unit signals for transmission to the remote station, the method is characterized in that it comprises the steps of: central transport, use the jump sequences to allow the respective conversion of the frequency jump signals to central station in fixed frequency signals of central unit that can be efficiently packaged within a pre-determined bandwidth before transmission to the remote transport unit; and in the remote transport unit, use the jump sequences to allow unpacking and respective conversion of the fixed frequency signals of the central unit packed into remote unit frequency hopping signals corresponding to the central station signals, before transmission to remote stations.

12. - The method according to claim 11, characterized in that the network comprises the Internet.

13. - The method according to claim 11, characterized in that the network comprises a local area network (LAN = Local Area Network).

14. - The method according to claim 11, characterized in that the network comprises a wide area network (WAN = Wide area Network).

15. - The method according to claim 11, characterized in that the network comprises a wired or wireless cable TV network.

16. - The method according to claim 11, > characterized in that the network comprises a video network.

17. The method according to claim 11, characterized in that the network comprises a network of optical fibers.

18. - The method according to claim 11, characterized in that the network comprises a point-to-point microwave network.

19. The method according to claim 11, characterized in that it further comprises the steps of: in the remote transport unit using the jump sequences to allow the respective conversion of the frequency hopping signals from the remote stations into the signals fixed-frequency remote unit that can be efficiently packaged within a predetermined bandwidth for transmission to the central transport unit; and in the central transport unit, use the jump sequence to allow the respective conversion of the fixed-frequency signals of the remote unit into central unit frequency hopping signals corresponding to the remote station signals for transmission to the central station .

20. The method according to claim 19, characterized in that the central station comprises a radio base station, the remote station comprises a mobile station and the jump sequences are transmitted from the base station to the mobile station on a radio channel. control .