Patent Publication Number: US-2006003760-A1

Title: Relay communication equipment, communication method and mobile communication system thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation of PCT/CN2004/000084, filed Jan. 29, 2004, which is incorporated herein by reference in its entirety, and also claims the benefit of Chinese Priority Application No. 03115211.2, filed Jan. 28, 2003. 
    
    
     FIELD OF THE TECHNOLOGY  
      The present invention relates to relay communication technology of a mobile communication system, more particularly to the relay communication equipment, relay communication method thereof and mobile communication system using this relay communication equipment, belonging to the time division duplex or frequency division duplex communication system fields.  
     BACKGROUND OF THE INVENTION  
      In the third generation mobile communication system, typical equipment comprises core network, base station controller (or rather radio network controller, RNC), wireless base station and user terminal, etc. In time division duplex (say TD-SCDMA system) or frequency division duplex mobile communication system, equipment with both user terminal functions and wireless base station functions is called relay equipment. Relay equipment are of important use in the following environments: in areas where it is difficult to set up optical fiber cable or electric wire between base station and RNC; when the established base station or optical fiber cable between base stations and RNC are damaged due to war, earthquake and natural disasters like flood, so that wireless mobile communication system of this area is paralytic; in a train, coach or closed carriage, when it&#39;s difficult for mobile communication users to communicate with mobile communication systems outside; in large buildings, when the penetrating power of electric wave is insufficient, and when there are many users and it&#39;s difficult for them to communicate with the outside. In the present mobile communication systems, repeaters are used to improve the covering in those areas with poor system coverage; in carriages of trains or automobiles, special terminal equipment (like truck-mounted terminals) are mainly used to solve some of the problems; in large buildings of the city, base stations are added or leaking antenna are set up. Employing this special terminal equipment will lead to a certain limitation for users in terms of using their own terminals, while it will need to establish electric cable, optical fiber cable or microwave link to use the repeaters or add base stations or set up leaking antenna, so that such technology is not flexible and difficult to implement.  
     SUMMARY OF THE INVENTION  
      The object of the present invention is to overcome the shortcoming of the prior art, provide a relay communication equipment as well as communication method thereof and mobile communication system that makes use of this equipment and method, wherein the relay communication equipment can communicate with terminals like the base station and can also communicate with base stations of the system like the terminal, without needing to set up electric cable or optical fiber cable to connect with the system, with fast and flexible disposition.  
      The present invention is implemented in one embodiment through the following technical scheme, and relay equipment of the present invention generally comprises: a terminal access function unit comprised of an independent antenna and feeder, a radio frequency transceiver and physical layer signal processing equipment, a base station function unit comprised of independent antenna and feeder, a radio frequency transceiver and physical layer signal processing equipment, a general control unit comprising digital signal processor, a control bus and high-rate data bus connecting the terminal access function unit and the general control unit, a control bus and high-rate data bus connecting the base station function unit and the general control unit; the terminal access function unit fulfilling the radio signal transmission and receiving between the relay equipment and mobile communication network, the terminal access function unit transmitting the data from the general control unit to the mobile communication network, wherein the data are transformed into radio signal after being orderly processed by the physical layer signal processing equipment and the radio frequency transceiver, and then transmitted to the air through the feeder and the antenna, the radio signal transmitted to the terminal access function unit by the mobile communication network being output to the general control unit in digital signal format after being orderly processed by the antenna and the feeder, the radio frequency transceiver and the physical layer signal processing equipment; the base station function unit fulfilling the radio signal transmission and receiving between the relay equipment and the mobile terminal, the base station function unit transmitting the data from the general control unit to the mobile terminal, wherein the data are transformed into radio signal after being orderly processed by the physical layer signal processing equipment, the radio frequency transceiver, the antenna and the feeder, and then transmitted to the air, the radio signal transmitted to the base station function unit by the mobile terminal being output to the general control unit in digital signal format after being orderly processed by the antenna and the feeder, the radio frequency transceiver and the physical layer signal processing equipment.  
      The terminal access function unit comprises: independent antenna and feeder, one or more than one radio frequency transceivers, one or more than one physical layer signal processing equipment, wherein at least one of the radio frequency transceivers are connected with the independent antenna and feeder, the physical layer signal processing equipment is connected with the radio frequency transceiver, the radio frequency transceiver can work with at least one carrier wave and multiple time slot, the physical layer signal processing equipment is comprised of special-purpose chip Alternate Special Integrated Circuit (ASIC) and programmable device to fulfill processing of physical layer signal in communication with conventional base stations of mobile communication network.  
      The base station function unit comprises an independent antenna and feeder, one or more than one radio frequency transceiver, one or more than one physical layer signal processing equipment, wherein the radio frequency transceiver is connected with the independent antenna and feeder to fulfill the processing of air access physical layer signal between the relay equipment and mobile user terminal in the local subnet (terminals in the covering area of the base station function unit), the physical layer signal processing equipment is connected with the radio frequency transceiver, the radio frequency transceiver can work with at least one carrier wave and multiple time slot. The physical layer signal processing equipment is comprised of a special-purpose chip Alternate Special Integrated Circuit (ASIC) and programmable device to fulfill processing of physical layer signal in communication with the mobile user terminal in the local subnet.  
      The general control unit comprises multiple digital signal processors, control bus, high-rate data bus, terminal voice and data interface, and Local Monitoring Terminal (LMT) interface. The general control unit processes high-layer signaling of terminal and base station, configures the equipment and manages wireless resource in the subnet according to commands of the mobile communication system, and monitors and controls the whole equipment operation. The general control unit possesses the control bus connected to the terminal access unit and the base station function unit; the general control unit provides the high-rate data bus connected to the terminal access unit and the base station function unit; the general control unit provides a signal switching function, so that the communication services in the local subnet can complete internal services without connecting to mobile communication system through the terminal access function unit so as to increase subnet capacity (generally, relay communication system communicates with actual terminal through the base station function unit, and the service data are forwarded to mobile communication system through the terminal function unit, then returned by mobile communication system, and service communication in local subnet is completed then). The general control unit provides terminal voice and data interface, so that this equipment is of a terminal&#39;s complete functions, and provides an interface for monitoring and managing Local Monitoring Terminal LMT.  
      The physical layer signal processing equipment inside the terminal access function unit and the physical layer signal processing equipment inside the base station function unit can be implemented independently or in combination.  
      The base station function unit supports terminal access of different wireless interface specification. The general control unit comprises a terminal voice and data interface, so that this equipment is of terminal&#39;s complete functions. The general control unit comprises interfaces for monitoring and managing Local Monitoring Terminal LMT. The digital signal processor may be, for example, a Micro-Controller Unit (MCU), Digital Signal Processor (DSP) or Alternate Special Integrated Circuit (ASIC).  
      The communication method for the relay communication equipment of the present invention comprises: 
          A. initialization: the terminal access unit of the relay communication equipment finding base station, sending access request to the base station, mobile communication network sending configuration information to the terminal access unit through downlink channel of the base station, the relay communication equipment configuring itself according to the configuration information;     B. the relay communication equipment subnet providing services: after the relay communication equipment finishing the initialization, the terminal access unit thereof keeping to monitor broadcast channel of the base station, and the base station function unit thereof providing services for those terminals in its covering area through subnet broadcast channel and other necessary downlink public channels; and     C. the relay communication equipment service terminating: when the relay communication equipment is not needed anymore to cover this area, the relay communication equipment sending information to the base station through the terminal access unit, starting the process of resource release, ending the service and deleting the subnet.        

      Before executing step A, the independent antenna and feeder part of the base station function unit in the relay communication equipment are placed in the expected covering area of the relay communication equipment, and the independent antenna and feeder part of the terminal access unit in the relay communication equipment are placed in the covering geographical area of the mobile communication network.  
      In step A, network transmits configuration information to the terminal access unit through a downlink channel of the base station, and the configuration information thereof comprises carrier frequency, maximum transmission power, service capacity, time slot or code channel for transmitting services with adjacent base stations.  
      In step B, in the covering area of the relay communication equipment, terminal finds the downlink public channel of this subnet, signals of the downlink public channel are from relay communication equipment; inside the covering area of the relay communication equipment, the terminal establishes, holds or releases the wireless connection with the relay communication equipment by taking use of wireless resources provided by the base station function unit of the relay communication equipment. If the communication destination of the terminal is another terminal and the two terminals in communication are both in the same subnet, the relay communication equipment finishes signal switching between these two terminals, charging-relevant information is transmitted to the base station through the terminal access unit of the relay communication equipment. If the communication destination of the terminal is a user outside this subnet, the relay communication equipment receives signals of the terminal through the base station function unit, after reprocessing the control information and service data thereof, transmits the reprocessed information to the base station through the terminal access unit, meanwhile receives information that is transmitted to the terminal by the base station through the terminal access unit, after reprocessing the control information and service data thereof, transmits the reprocessed information to the terminal through the base station function unit.  
      The mobile communication system utilizing the relay communication equipment of the present invention comprises at least one terminal, at least one base station and at least one relay communication equipment; the relay communication equipment at least comprises one terminal access unit and one base station function unit, and covers a certain geographical area, the terminal and the base station function unit of the relay communication equipment mutually transmit and receive radio signals in the geographical covering area of the relay communication equipment, the base station can cover a certain geographical area, the relay communication equipment and the base station mutually transmit and receive radio signals in the geographical covering area of the base station through the terminal access unit, the terminal establishes, holds and releases the wireless connection with the relay communication equipment in the geographical covering area of the relay communication equipment, the relay communication equipment establishes, holds and releases the wireless connection with the base station in the geographical covering area of the base station.  
      The terminal detects the signal transmitted on downlink public channel by the relay communication equipment in the geographical covering area of the relay communication equipment, and assumes this signal is transmitted by common base station. The terminal can establish, hold and release the wireless connection by making use of the method for establishing, holding and releasing wireless connection with a common base station.  
      During the period when the terminal and the relay communication equipment are in connection, according to the different communication destinations, if the communication target terminal is inside subnet, the relay communication equipment takes charges of signaling, data processing and switching between the two terminals; if the communication target terminal is outside the subnet, the relay communication equipment takes charge of signaling, data processing and forwarding between the terminal and the base station.  
      The operation mode of the present invention will be described by taking time division duplex mobile communication system. Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system of the third generation mobile communication has multiple time slot structure; both uplink and downlink of each time slot can be set by the system. Taking TD-SCDMA standard for example, the subnet provided by this relay communication equipment can be considered as a cell in mobile communication network, and the user terminal&#39;s operation modes in this subnet and in mobile communication network are the same. After the relay communication equipment is installed, adjacent base stations are searched and access is applied for. When the operation is started, the base station function unit cannot transmit signal. At first the terminal access unit must search adjacent base stations, and apply to access like common terminals, and then put forward the operation application of this relay communication equipment while applying for access. After this application is accepted by the system, the system will configure this relay communication equipment, namely configuring those indispensable parameters such as operation carrier frequency, maximum transmission power electric level, service capacity, time slot or code channel for transmission service among base stations. After the relay communication equipment acquires the configuration, subnet starts working, by using the terminal access unit thereby, the relay communication equipment will receive the signals transmitted by base stations in the network through Broadcast Channel and Paging Channel (BCCH and PCH), and can forward all or part of the channel&#39;s information through the self broadcast channel of the base station function unit thereof, or generate self broadcast information and send the information through broadcast channel. As for the terminals in covering area of this subnet, this subnet (relay communication equipment) is considered as a common base station, wherein subnet and terminals communicate in completely the same way. As to the relay communication equipment with switching function, the working mode can be set like this: communications among terminals inside this subnet (either voice or data service) are switched inside this relay communication equipment, only charging information rather than service data is transmitted to the system, in order to increase system capacity; as to communications between terminals inside this subnet and outside this subnet (either voice or data service), this relay communication equipment just plays forwarding role, the communications are forwarded to the adjacent base station through service time slot (code channel) between the relay communication equipment and the adjacent base station, and connected to the system through the adjacent base station, wherein the working mode is the same as that for implementing common service. After one communication is finished, the system or relay communication equipment will release the resource for other users&#39; use.  
      The present invention is of substantial and distinct improvement. Equipment of the present invention can place the antenna and feeder of base station function part in the area that is not covered by mobile communication network, so that common user terminals can acquire mobile communication service in this area. Equipment of the present invention can also quickly provide services for those areas with urgent need for mobile communication service. The present invention can also greatly improve system&#39;s covering condition, so that mobile communication users on the train or coach can communicate freely in travel and make the users in large buildings acquire the services conveniently.  
      These and other aspects of the present invention are more fully described herein.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:  
       FIG. 1  is a flowchart illustrating how to set relay communication equipment for mobile communication network;  
       FIG. 2  is a framework illustrating relay communication equipment structure of the present invention; and  
       FIG. 3  is the basic operating flowchart of relay communication equipment of the present invention.  
    
    
     EMBODIMENTS OF THE INVENTION  
      The present invention now will be described more fully with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.  
      The application distribution of relay communication equipment of the present invention in mobile communication system is shown in  FIG. 1 , wherein part of the system&#39;s conventional base stations like  221 ,  222 ,  223 , . . . ,  22   n  are connected with base station controller  20  in cable or wireless mode and cover certain areas. Mobile communication service is implemented in these covered areas. However other areas like  231 ,  232 , . . . ,  23   m  cannot be covered by conventional base stations. In such areas, relay communication equipment of the present invention can be applied, like  241 ,  242 , . . . ,  24   k , wherein antennas of the terminal access units of these relay communication equipments are set up in the covered areas of convention base stations  222 ,  223 , . . . ,  22   n ; while antennas of base station function units of relay communication equipments can cover the areas that cannot be covered by the conventional base stations, so that subnets are established one by one. User terminal&#39;s working mode in areas covered by subnet and that in areas covered by conventional base station are the completely the same. It is obvious that the relay communication equipment expands and improves the covering of mobile communication network. Since the relay communication equipment can be mounted on mobile objects, such as the trains and coaches, a subnet can be established inside the closed carriage and performance of the mobile communication network can be improved. In  FIG. 1, 21  denotes a base station controller and  10  denotes a system network side.  
      One embodiment of the equipment framework of the present invention is shown in  FIG. 2 , generally comprising: terminal access function unit  1 , independent antenna and feeder  2 , radio frequency transceiver  3 , physical layer signal processing equipment  4 , base station function unit  5 , independent antenna and feeder  6 , radio frequency transceiver  7 , physical layer signal processing equipment  8 , general control unit  9 , digital signal processor  10 , control bus  11  and high-rate data bus  12 , wherein general control unit  9  is connected with terminal access function unit  1  through high-rate data bus  12  and control bus  11 , also connected with base station function unit  5  through high-rate data bus  12  and control bus  11 .  
      Terminal access function unit  1  receives and transmits radio signals between the relay communication equipment and mobile communication network, terminal access function unit  1  transmits data from general control unit  9  to a mobile communication network, after being processed by physical layer signal processing equipment  4 , radio frequency transceiver  3 , independent antenna and feeder  2 , the data are transformed into radio signals and sent to the air, after being processed by independent antenna and feeder  2 , radio frequency transceiver  3  and physical layer signal processing equipment  4 , the radio signals that the mobile communication network transmits to terminal access function unit  1  are output to general control unit  9  in digital signal format.  
      Base station function unit  5  receives and transmits the radio signals between the relay communication equipment and mobile terminal. Base station function unit  5  transmits data from general control unit  9  to a mobile terminal, and after being processed by physical layer signal processing equipment  8 , radio frequency transceiver  7 , independent antenna and feeder  6 , the data are transformed into radio signals and sent to the air, after being processed by independent antenna and feeder  6 , radio frequency transceiver  7  and physical layer signal processing equipment  8 , the radio signals that the mobile terminal transmits to base station function unit  5  are output to general control unit  9  in digital signal format.  
      Terminal access function unit  1  comprises an independent antenna and feeder  2 , one or more than one radio frequency transceiver  3 , one or more than one physical layer signal processing equipment  4 , wherein radio frequency transceiver  3  is connected with independent antenna and feeder  2 , physical layer signal processing equipment  4  is connected with radio frequency transceiver  3 , radio frequency transceiver  3  can work with at least one carrier wave and multiple time slot, physical layer signal processing equipment  4  is comprised of special-purpose chip Alternate Special Integrated Circuit (ASIC) and programmable device to fulfill processing of physical layer signal in communication with conventional base stations of mobile communication network.  
      Base station function unit  5  comprises an independent antenna and feeder  6 , one or more than one radio frequency transceiver  7 , one or more than one physical layer signal processing equipment  8 , wherein radio frequency transceiver  7  is connected with independent antenna and feeder  6  to fulfill the processing of air access physical layer signal between the relay equipment and mobile user terminal in the local subnet, physical layer signal processing equipment  8  is connected with radio frequency transceiver  7 , radio frequency transceiver  7  can work with at least one carrier wave and multiple time slot. Physical layer signal processing equipment  8  is comprised of special-purpose chip Alternate Special Integrated Circuit (ASIC) and programmable devices to provide processing of physical layer signal in communication with mobile user terminal in the local subnet.  
      General control unit  9  comprises multiple digital signal processors  10 , control bus  11 , high-rate data bus  12 , terminal voice and data interface  13  and  14 , and Local Monitoring Terminal (LMT) interface  15 . General control unit  9  processes high-layer signaling of terminal and a base station, configures the equipment and manages wireless resource in a subnet according to command of mobile communication system, and monitors and controls the whole equipment operation. General control unit possesses the control bus  11  connected to both terminal access unit  1  and base station function unit  5 . General control unit  9  provides the high-rate data bus  12  connected to both terminal access unit  1  and base station function unit  5 . General control unit  9  provides signal switching function, so that the communication services in local subnet can complete internal services without connecting to mobile communication system through the transiting terminal access function unit, and increase subnet capacity. Namely, after arriving at general control unit  9 , the service information from base station function unit is switched and directly returned to the target terminal through the base station function unit, skipping the communication service data loop course between the terminal access function unit and mobile communication system, so that wireless resource of this part is saved. General control unit  9  provides terminal voice and data interface  13  and  14 , so that this equipment is of terminal&#39;s complete functions, and provides interface for monitoring and managing Local Monitoring Terminal LMT interface  15 .  
      The communication method adopting the relay communication equipment of the present invention is as follows:  
      A. initialization: terminal access unit  1  of the relay communication equipment finds the base station, and sends access request to the base station. The network sends configuration information to the terminal access unit through downlink channel of this base station, wherein the configuration information comprises carrier frequency and maximum transmission power, etc. The relay communication equipment configures itself according to the configuration information.  
      B. the relay communication equipment provides subnet services. After the initialization, the relay communication equipment keeps monitoring broadcast channel of the base station through terminal access unit  1 , and the base station function unit  5  thereof provides services for those terminals in its covering area through subnet broadcast channel and other necessary downlink public channels.  
      In the covering area of the relay communication equipment, the terminal can detect downlink public channel of this subnet, and assumes that signals of the downlink public channel are from one base station, namely in terms of the terminal, the relay communication equipment is a common base station. By making use of the wireless resource provided by base station function unit  5  of the relay communication equipment, the terminal can establish, hold or release wireless connection with the relay communication equipment in the covering area of the relay communication equipment. Here, according to different destinations of terminal communication, there are two operation modes for the relay communication equipment:  
      First, communication destination of the terminal (source terminal) is a terminal user inside the subnet (destination terminal), namely this destination terminal is also in the covering area of the relay communication equipment and is holding a wireless connection with the relay communication equipment, namely the two terminals in communication are both in the subnet, then the relay communication equipment implements signal switching between the two terminals, here the charging-relevant information can be transmitted to the base station in mobile communication system (base station near the relay communication equipment) through base station function unit  5  of the relay communication equipment, but service information may not be transmitted to this base station in mobile communication system.  
      Second, communication destination of the terminal (source terminal) is a terminal user outside the subnet (destination terminal), then the relay communication equipment receives signals of the source terminal through base station function unit  5 , and after reprocessing the control information and service data thereof, transmits the information to a base station in the mobile communication system (base station near relay communication equipment) through terminal access unit  1 ; meanwhile, the relay communication equipment receives the information that this base station transmits to the destination terminal through terminal access unit  1 , and after reprocessing the control information and service data, transmits the reprocessed information to the destination terminal through base station function unit  5 .  
      C. the relay communication equipment service terminates. When the relay communication equipment is not needed anymore to cover this subnet area, the relay communication equipment sends information to the base station through terminal access unit  1 , starts the process of resource release, ends the service and deletes the subnet.  
      A mobile communication system adopting the relay communication equipment of the present invention is comprised of at least a terminal, at least a conventional base station, and at least a relay communication equipment, wherein the relay communication equipment at least comprises a terminal access unit and a base station function unit, and covers a certain geographical area. The terminal and base station function unit  5  of the relay communication equipment mutually transmit and receive radio signals in the geographical covering area of the relay communication equipment. The conventional base station can cover a certain geographical area, the relay communication equipment and the conventional base station mutually transmit and receive radio signals in the geographical covering area of the conventional base station through terminal access unit  1 , the terminal establishes, holds and releases the wireless connection with relay communication equipment in the geographical covering area of the relay communication equipment, the relay communication equipment establishes, holds and releases the wireless connection with the conventional base station in the geographical covering area of the conventional base station.  
      In the geographical covering area of the relay communication equipment, the terminal detects the signal transmitted on downlink public channel of the relay communication equipment, and assumes this signal is transmitted by common base station. The terminal can establish, hold and release the wireless connection by making use of the method for establishing, holding and releasing wireless connection with a common base station.  
      During the period when the terminal and relay communication equipment are in connection, according to the different communication destinations, if the communication target terminal is inside subnet the relay communication equipment takes charge of signaling, data processing and switching between the two terminals; if the communication target terminal is not inside the subnet, the relay communication equipment takes charge of signaling, data processing and forwarding of information between the terminal and the base station.  
      The working mode of relay communication equipment of the present invention is shown in  FIG. 3 , the working mode thereof is illustrated by taking a time division duplex mobile communication system, for example, in the present invention. In the third generation mobile communication TD-SCDMA system, the time slot is of multiple structure, uplink and downlink of each time slot can be set by the system. Taking TD-SCDMA standards for example, the subnet provided by the relay communication equipment can be considered as a cell in mobile communication network, a user terminal&#39;s working mode in this subnet and user terminal&#39;s working mode in mobile communication network are the same.  
      Step  41 : after the relay communication equipment is installed, adjacent base stations are searched and access is applied for. When the operation is started, the base station function unit cannot transmit a signal, at first the terminal access unit must search adjacent base stations and apply for access like common terminals, and then put forward the operation application of this relay communication equipment while applying for access.  
      Step  42 : after this application is accepted by the system, the system will configure the relay communication equipment, namely configuring parameters such as operation carrier frequency, maximum transmission power electric level, service capacity, time slot or code channel for transmission service between adjacent base stations.  
      Step  43 : after the relay communication equipment acquires the configuration, and the subnet starts working, by using the terminal access unit thereby, the relay communication equipment will receive the signals transmitted by adjacent base stations in the network through Broadcast Channel and Paging Channel (BCCH and PCH), and can forward all or part of the channel&#39;s information through the self broadcast channel using the base station function unit thereof, or generate self broadcast information and send the information through broadcast channel.  
      Step  44 : As for the terminals in covering area of this subnet, this subnet (relay communication equipment) is considered as a common base station, wherein subnet and the terminal communicate in completely the same way. There may be two kinds of situations as shown in steps  45  and  46  of  FIG. 3 .  
      Step  45 : as to the relay communication equipment with switching function, the working mode can be set by having: communications with terminals inside this subnet (either voice or data service) switched inside this relay communication equipment, only charge-related information rather than service data is transmitted to the system, in order to increase system capacity.  
      Step  46 : as to communications between terminals inside this subnet and outside this subnet (either voice or data service), the relay communication equipment plays a forwarding role, the communications are forwarded to the adjacent base station through a service time slot (code channel), and connected to the system through an adjacent base station, wherein the working mode is the same as that for implementing common service.  
      Step  47 : after one communication is finished, the system or relay communication equipment will release the resource for other users&#39; use.  
      In the present invention, with reference to mobile communication system of time division duplex and taking one of the third generation mobile communication standards TD-SCDMS for example, technological characters relevant to the relay communication equipment are illustrated. After being properly and equally transformed, technological characters of the present invention are also applicable in systems of other time division duplex or frequency division duplex mobile communication standards.  
      Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions. Accordingly, it should be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended exemplary inventive concepts. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.