EP1092277A1

EP1092277A1 - Method for communicating between a first communication unit and a second communication unit

Info

Publication number: EP1092277A1
Application number: EP99911485A
Authority: EP
Inventors: Ranjan Dasgupta; Vernon W. Hamlin
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1998-06-29
Filing date: 1999-03-19
Publication date: 2001-04-18
Also published as: EP1092277A4; WO2000001083A1

Abstract

The present invention provides a method for communicating between a first communication unit (111) and a second communication unit (112). The first communication unit (111) is in communication with an IP radio (141) that is connected to a base transceiver station controller (131). The BTS controller (131) is connected to a base station controller (121). The IP radio (141) is coupled to an external network (104) via an IP-enabled local area network (LAN) interface (171). The first communication unit (111) transmits a signal to the IP radio (141), which receives the signal. The signal is routed to the second communication unit (112) through the external network (104) via the IP-enabled local area network (LAN) interface (171).

Description

METHOD FOR COMMUNICATING BETWEEN A FIRST COMMUNICATION UNIT AND A SECOND COMMUNICATION UNIT

Field of the Invention

The present invention relates generally to communication systems, and more particularly to a communication system including a connection to an external network.

Background of the Invention

Communication systems allow the transfer of signals, such as voice signals, data signals, or control signals, between communication units, such as cellular telephones. This communication often happens between communication units that are located at different cell sites, often sites that are geographically distant from each other. Each cell site typically comprises cellular infrastructure equipment, such as transceivers, BTS controllers, Mobile Switching Centers (MSCs) , and other cellular equipment. In order to transfer the signal received from the transmitting communication unit to the receiving communication unit, the communication system needs to send the data from the IP radio in communication with the transmitting communication unit to the IP radio associated with the receiving communication unit.

The IP radios need to transfer the signals over a communication line. When the IP radios are local to each other, the communication line can be a LAN fabric such as 10/100BaseT. When the IP radios are remote from each other, the communication line can be El/Tl, Frame Relay, Asynchronous Transfer Mode (ATM), X.25, or wireless microwave links. In either case, the transmission of signals between remote IP radios leads to costly implementations of hardware. All cell sites have to be in some way connected to such landline or over the air communication connections, which lead to increased costs associated with operating a cellular system. In addition, the addition of a new cellular site requires the installation of additional hardware to allow the cellular site to communicate with other cellular sites in the communication system. Consequently, a need exists for a method for providing communication between communication units that allows for easy and inexpensive communication between communication units in a communication system.

Brief Description of the Drawings

FIG. 1 depicts a communication system in accordance with the preferred embodiment of the present invention; FIG. 2 depicts a flow diagram for sending a signal from a first communication unit to a second communication unit utilizing an IP-enabled LAN interface in accordance with the preferred embodiment of the present invention; FIG. 3 depicts a flow diagram for sending a signal that includes a voice portion and a data portion from a first communication unit to a second communication unit in accordance with the preferred embodiment of the present invention;

FIG. 4 depicts a high-level representation of the communication system of FIG. 1 in accordance with the preferred embodiment of the present invention;

FIG. 5 is an architectural representation of a communication unit and an IP radio in accordance with the preferred embodiment of the present invention; and

FIG. 6 depicts a bituple that facilitates handoff in accordance with the preferred embodiment of the present invention.

Detailed Description of a Preferred Embodiment

The present invention provides a method for communicating between a first communication unit and a second communication unit. The present invention provides for this communication by connecting cellular infrastructure equipment, such as IP radios, BTS controllers, and base station controllers (BSCs) , to an external network, such as the internet. This connection is facilitated by connecting an IP-enabled LAN interface to the cellular infrastructure equipment to provide access to the external network. The following is a list of acronyms used in this application:

BTS Base Transceiver Station BSC Base Station Controller HLR Home Location Register IP Internet Protocol

LAN Local Area Network VLR Visitor Location Register WAN Wide Area Network The present invention can be better understood with reference to FIGs. 1-6. FIG. 1 depicts a communication system 100 in accordance with the preferred embodiment of the present invention. System 100 includes three cellular sites, a first cell site 101, a second cell site 102, and a third cell site 103. Each cell site 101-103 includes a BSC, a plurality of IP radios, a BTS controller, and an IP-enabled LAN interface, commonly referred to as an IP gateway. The IP gateway provides connection to an external network, such as the internet, as depicted in FIG. 1. The external network alternately comprises a data network, a voice network, or a combination data/voice network. Each of the three cellular sites 101-103 depicted in FIG. 1 provides connection to external network 104 at different points within cell sites 101-103.

First cell site 101 includes first BSC 121. First BSC 121 controls processing of calls at first cell site 101. First cell site 101 preferably includes an HLR 116 and a VLR 126 coupled to first BSC 121. HLR 116 and VLR 126 can also be assigned a unique IP address. BSC 121 is coupled to first BTS controller 131. BSC 121 can be connected to BTS controller 131 through a WAN interface. BTS controller 131 provides control of transceivers 141, 151, and 161. BTS controller 131 is coupled to transceivers 141, 151, and 161 through IP LAN 181. Transceivers 141, 151, and 161 are also referred to as IP radios. IP LAN 181 also provides connection between IP radios 141, 151, and 161. IP gateway 171 provides interconnection to an external network, such as to internet 104. In the configuration as depicted at cell site 101, the connection to external network 104 is provided by IP gateway 171 through IP LAN 181. Alternately, the functions performed by IP gateway 171 can be accomplished by assigning an IP-enabled router address to an IP radio 141, 151, or 161. The IP-enabled router address is a unique IP address that enables any processor on the internet to identify and communicate with the apparatus connected to the network. In the alternate embodiment, the cell site equipment performs its assigned function and additionally doubles as an IP router for cell site 101. In this manner, for an in- building type of system, it may be convenient to provide a gateway connection that is coupled to the subnet that connects the IP-enabled transceivers. This allows for the most direct form of internet connectivity and also for higher bandwidths . This is readily accomplished in an in-building scenario, since it is convenient to locate a gateway off the subnet and route data through to the internet.

Second cell site 102 includes second BSC 122, which performs similar functions as first BSC 121. Second cell site 102 preferably includes an HLR 117 and a VLR 127 coupled to first BSC 121. HLR 117 and VLR 127 can also be assigned a unique IP address. BSC 122 is coupled to second BTS controller 132. BTS controller 132 provides control of BTSs 142, 152, and 162. BTS controller 132 is coupled to BTSs 142, 152, and 162 through IP LAN 182, which provides interconnection therebetween. IP gateway 172 provides connection to an external network, such as to internet 104. In the configuration as depicted at cell site 102, the connection to external network 104 is provided by IP gateway 172 through BTS controller 132. Alternately, the functions performed by IP gateway 172 can be accomplished by assigning an IP-enabled router address to BTS controller 132. This router address provides for routing to BTS controller from any device connected to the external network, such as the internet. In the alternate embodiment, the cell site equipment performs its assigned function and additionally doubles as an IP router for cell site 102.

In this manner, an improved communication system is provided. In the case of a conventional macro-cell, an internet connection may be more difficult to achieve. In this situation, the IP-enabled transceiver connects to a control unit over a LAN or cPCI interface, which is in turn connected to BSC controller 122. Gateway 172 may be located here, since BSC 122 is likely at a centralized site where internet connections are more readily available. In addition, utilizing this embodiment allows multiple BTS sites to be served by IP gateway 172. BTS controller 132 is coupled to IP radios 142, 152, and 162 through an IP-enabled LAN interface. Third cell site 103 includes third BSC 123, which performs similar functions as first BSC 121. Third cell site 103 preferably includes an HLR 118 and a VLR 128 coupled to third BSC 123. HLR 118 and VLR 128 can also be assigned a unique IP address. Third BSC 123 is coupled to third BTS controller 133. BTS controller

133 provides control of transceivers 143, 153, and 163. BTS controller 133 is coupled to IP radios 143, 153, and 163 through IP LAN 183. IP LAN 183 provides interconnection between BTSs 143, 153, and 163. IP gateway 173 provides interconnection to an external network, such as to internet 104. In the configuration as depicted at cell site 103, the connection to external network 104 is provided by IP gateway 173 through BSC 123. Alternately, the functions performed by IP gateway 173 can be accomplished by assigning an IP-enabled router address to BSC 123. In this configuration, the cell site equipment performs its assigned function and additionally doubles as an IP router for cell site 103.

IP radios 141-143, 151-153, and 161-163 each include a transceiver that includes a transmitter and a receiver. Each such IP radio 141-143, 151-153, and 161-163 is controlled by a BTS controller 131-133, respectively. The transceiver transmits, over-the-air, RF signals to be received by communication units 111- 113. The transmission is well-known in the art, and will not be described further in this application. The transceivers 108 receive messages from communication units 111-113, as is well known in the art.

Communication units 111-113 are preferably cellular telephone units that are capable of communicating with IP radios 141-143, 151-153, and 161- 163. Communication units 111, 112, and 113 include a transceiver 191, 192, and 193, respectively, that includes a transmitter and a receiver, as is well-known in the art. Communication units 111-113 communicate with IP radios 141-143, 151-153, and 161-163 by transmitting messages by the transceivers 191-193 located therein, and by receiving messages generated by IP radios 141-143, 151-153, and 161-163 at transceivers 191-193 located therein. FIG. 2 depicts a flow diagram for communicating between a first communication unit and a second communication unit, such as between communication units 111-113. The first and second communication units can be mobile units, such as cellular telephones, laptop or palmtop computers, or landline units, such as landline telephones, landline connected desktop computers, and any other communication device that requires communication with a second communication device.

The first communication unit transmits (201) a signal intended for the second communication unit to a first IP radio. The first signal can be a voice signal, a data signal, or a combination voice/data signal that includes a voice portion and a data portion. The first IP radio received (203) the signal from the first communication unit. The signal is routed to the second communication unit through the external network via the IP-enabled local area network (LAN) interface. This is accomplished by determining which piece of equipment is connected to the IP-enabled LAN interface.

The first IP radio determines (205) whether it is connected to the IP gateway. This determination is accomplished by checking a database that includes configuration information relating to the cell site. If the first IP radio is connected to the IP-enabled LAN interface, the first IP radio sends (207) the signal to the IP-enabled LAN interface. If the first BTS is not connected to the IP gateway, it is determined (209) if the BTS controller is connected to the IP-enabled LAN interface. If the BTS controller is connected to the IP gateway, the first BTS sends (211) the signal to the BTS controller. The BTS controller then sends (213) the signal to the IP-enabled LAN interface to be sent to the second communication unit. If the BTS controller is not connected to the IP- enabled LAN interface, it is determined (215) whether the BSC is connected to the IP-enabled LAN interface. If the BSC is not connected to the IP gateway, the signal is sent (223) to the second communication unit in the conventional way, as is known in the art. The process then ends (299) .

If the BSC is connected to the IP gateway, the first IP radio sends (217) the signal for the BTS controller. The BTS controller sends (219) the signal to the BSC, which in turn sends (221) the signal to the IP-enabled LAN interface.

Upon sending the signal to the IP-enabled LAN interface, at step 207, 213, or 221, the IP-enabled LAN interface sends (225) the signal from the IP gateway to the second communication unit. In an IP network, the routing of packets through the network is part of the functionality built into the IP protocol. Intermediate nodes, such as routers, include routing tables and other built-in intelligence that allows IP packets to follow an optimal path to the final destination. The process then ends (299) .

FIG. 3 depicts a flow diagram for communicating between a first communication unit and a second communication unit. FIG. 3 depicts an embodiment of the invention where the signal includes both a voice portion and a data portion and where the voice portion is given priority over the data portion. The first communication unit transmits (301) a signal intended for the second communication unit to a first IP radio. In the embodiment depicted in FIG. 3, the signal includes a voice portion and a data portion. The first BTS received (303) the signal from the first communication unit. The signal is routed to the second communication unit through the external network via the IP-enabled local area network (LAN) interface. This is accomplished by determining which piece of equipment is connected to the IP-enabled LAN interface.

The first IP radio determines (305) whether it is connected to the IP gateway. This is accomplished by checking against a database that includes configuration information that relates to the cell site. One method used to determine whether an IP-enabled transceiver is connected to an external gateway is to execute an IP "ping" command to a well-known external site. In this case, the ping command can be directed at the external IP gateway itself. If the first IP radio is connected to the IP-enabled LAN interface, the first IP radio sends (307) the signal to the IP-enabled LAN interface. If the first IP radio is not connected to the IP gateway, it is determined (309) if the BTS controller is connected to the IP-enabled LAN interface. If the BTS controller is connected to the IP gateway, the first IP radio sends (311) the signal to the BTS controller. The BTS controller then sends (313) the signal to the IP-enabled LAN interface to be sent to the second communication unit. If the BTS controller is not connected to the IP-enabled LAN interface, it is determined (315) whether the BSC is connected to the IP-enabled LAN interface. If the BSC is not connected to the IP gateway, the signal is sent (323) to the second communication unit in the conventional way, as is known in the art. The process then ends (399).

If the BSC is connected to the IP gateway, the first IP radio sends (317) the signal for the BTS controller. The BTS controller sends (319) the signal to the BSC, which in turn sends (321) the signal to the IP-enabled LAN interface.

Upon sending the signal to the IP-enabled LAN interface, at step 307, 313, or 321, the IP-enabled LAN interface determines (325) if there is a need to send the voice portion of the signal first. Voice signals are inherently real-time, and a delay in a particular voice packet renders it substantially useless. This is due to the fact that a segment of voice cannot be replayed after the succeeding voice segments have been played. Consequently, voice packets need to be assigned a higher "Quality of Service" categorization as compared to data, such that the voice packets have a higher priority than data packets. If the voice portion is to be given priority over the data portion, the IP-enabled LAN interface sends (327) the voice portion of the signal to the second communication unit through the external network. The process then ends (399) . If the voice portion is not to be given priority over the data portion, the IP gateway sends (329) the signal, including both the voice portion and the data portion, to the second communication unit through the external network. The process the ends (399) . As an example of the operation of the present invention, communication unit 111 transmits a signal to IP radio 141. The signal can be a voice signal, a data signal, a control signal, or a combination thereof. The signal is transmitted over the air between transceiver 191 and a transceiver located at IP radio 141.

As depicted in FIG. 6, the signal includes a bituple 601. Bituple 601 includes a communication unit identification (ID) 603 and an IP radio identification 605. Communication unit ID 603 is associated with and identifies communication unit 111. IP radio ID 605 is associated with IP radio 141 and identifies IP radio 141. When traveling through site 101, communication unit 111 may handoff to IP radio 151, as is known in the art. This handoff process is facilitated by use of bituple 601. To handoff to IP radio 151, communication unit 111 changes IP radio ID 605 within bituple 601 to a value associated with IP radio 151. This value can be the serial number of IP radio 151, the frequency of IP radio 151, or any other characteristic that uniquely identifies IP radio 151. Upon receiving the bituple including the IP radio ID for IP radio 151, IP radio 141 hands off processing of the call to IP radio 151. Returning now to the processing of a communication, upon receiving a signal from communication unit 111, IP radio 141 determines the destination of the signal. For example, the signal may be destined for communication unit 112 currently located at site 102. IP radio 141 will route the signal, after determining that it is connected to IP gateway 171 through IP LAN 181, the signal to IP gateway 171. IP gateway 171 will determine the destination of the signal by looking at the IP address of the destination, i.e. IP radio 152 located at site 102. IP gateway 171 then sends the signal through external network 104, such as the internet. The signal is routed based upon the unique IP address located within the signal. The signal is ultimately routed to IP gateway 172 located at site 102. IP gateway 172 then sends the signal to BTS controller 132, which determines which IP radio the signal is sent to. BTS controller 132 then forwards the signal to IP radio 152, which subsequently sends the signal, over the air, to communication unit 112. Processing of other signals proceeds in a similar manner.

FIG. 4 depicts an IP-based digital wireless infrastructure network 400 in accordance with the preferred embodiment of the present invention. FIG. 4 depicts a wireless infrastructure network 400 uses the IP protocol for its internal operations. IP-enabled transceiver units 413 and 414 that enable communications with a communication unit, such as a mobile station 415 and a mobile terminal 419, respectively. Communication units 415 and 419 are effective to transmit either traditional voice packets or IP packets to IP radios 413 and 414, respectively. IP radios 413 and 414 interface with IP-based GSM network 409 through the use of an IP-enabled interface, BSC/BTS server 407 is a network control unit that administers and controls a set of IP-enabled transceiver units. BSC/BTS server 407 preferably runs all of the call processing software and a part of the SS7 protocol required to interface with MSC 403 and PSTN 401. The traditional interfaces to PSTN 401 are provided through MSC 403 and an IP-based transcoder unit 405. The control protocol used for this connection is SS7. The SS7 protocol stack is preferably distributed between transcoder unit 405, which runs levels 1 and 2, and BSC/BTS unit 407, which runs level 3 (SS7/MTP) .

IP-based transcoder unit 405 acts as a gateway between the IP-based network 409 connecting the IP- enabled transcoders and BSC/BTS node 407 and MSC 403.

Consequently, IP-based transcoder unit 405 communicates to a packet-switched network on the IP side, and to a TDM network on the MSC/PSTN side. As explained previously, IP-based transcoder unit 405 implements a part of the SS7 protocol stack.

IP-enabled transceiver units 413 and 414 provide direct wireless IP functionality to a communication unit, such as mobile station 415 and mobile terminal 419. This provides numerous improvements over the prior art.

One such improvement over the prior art is direct internet access for mobile communication units. An IP call placed through wireless mobile communication unit 419 for purposes of accessing the internet 421 can be routed as follows. Each IP packet transmitted by communication unit 419 is regenerated at the IP-enabled transceiver unit 414 by a method described with reference to FIG. 5 below. Each IP packet is then routed by IP radio 414 over its terrestrial IP link, preferably a 100BaseT LAN connection, to an Internet gateway device 417, which is connected to the Internet 421. IP radio 414 acts as a local IP gateway for communication unit 419, while internet gateway 417 acts as the external router/gateway device, configured with firewall and proxy services as needed. Once the IP packets are delivered to the internet 421, they are automatically routed to any destination server, such as internet content provider 423, that the mobile user 419 is interested in accessing. Downlink IP packets will follow a similar reverse path to reach mobile communication unit 419.

A further advantage of the present invention is the ability to have a locally routed IP voice call. In this scenario, voice information is encapsulated in IP packets, and allowed to travel to its destination through the use of IP routing. The end destination may be a laptop computer 411 directly attached to infrastructure 409, a mobile phone 415 or a wireline phone 410 attached to the wireless infrastructure 409 via an IP-based PBX device 408. In all these scenarios, the traditional means of routing a voice call through transcoder 405 and Mobile Switching Center 403 and possibly onto PSTN network 401 is bypassed by routing the call directly and locally to its destination, via IP network 409.

Traditional voice calls will be forwarded to IP- enabled transcoder device 405, which is capable of transcoding IP voice packets into 64 kbps TDM channels, compatible to PSTN network 401 and onto a traditional wireline phone device.

FIG. 5 depicts the data flow of an IP connection between a mobile computing device 419 and an IP-enabled transceiver unit 414. In order to provide a direct IP connection between a mobile computing device 501 and its final destination, it is necessary for the IP- enabled transceiver unit to which mobile device 501 is communicating to regenerate the IP packet transmitted by mobile communication unit 501. The following text traces the path of an uplink IP packet through its journey from an IP-based application 502 running on mobile communication unit 501 until it gets routed to the Internet 421. This implementation assumes the use of the wireless GSM standard for mobile communications. An IP-based application 502 uses either a TCP 506 or a UDP 504 based socket to communicate to its peer application located on a server on internet 421. Each TCP or UDP packet generated by application 502 is processed by IP protocol layer 508 on mobile communication unit 501. The connection between mobile communication unit 501 and mobile station 521, preferably a portable GSM phone, is via an asynchronous media such as a RS-232 serial link. Accordingly, the PPP protocol 510 is used to encapsulate each IP packet, and generate a bit-stream to mobile station 501, after performing the necessary rate adaptation at RA1 layer 511. The Rate Adaptation layer 511 passed the packet to async layer 512, which communicates the packet to mobile station 521.

The bit-stream is then passed through to mobile station 521, where it is processed by the Radio Link Protocol 520 and through rate adaptation layers 522, before it is transmitted over the air as GSM TRAU packets via the RF unit 526. The over-the-air packets are then received by an RF unit 532 located at the IP- enabled transceiver unit 531, where they are again passed through rate adaptation layers 530, in order to regenerate the transmitted TRAU packets.

The TRAU packets are then passed from the RF unit 531 to a computer device 541 within the IP-enabled transceiver unit 414, using a suitable packet bus such as compact PCI 534. Upon reaching compute device 541, the TRAU packets are read into RLP stack 548 process through RF interface device driver 550. After RLP processing, PPP protocol 546 is terminated, at which point the original IP packets are regenerated. These packets are then injected back into IP protocol layer 542 through the use of tunnel driver 546. Upon reaching IP protocol layer 542, the packets are routed out through LAN interface 560 to an external IP gateway device 417, which routes the packets onto the internet 421.

The present invention thereby provides numerous advantages and benefits over the prior art through the use of an IP-enabled transceiver for direct internet access. By using an IP-enabled transceiver as the primary wireless communication unit, the mobile computing device is directly connected to the internet, or other data network of choice, via the transceiver, which acts as the data-network gateway. As the mobile user moves, the call is handed over to similar IP- enabled transceivers that service the wireless cell local to the mobile user, which in turn acts as the data-network gateway. Consequently, the only cost of providing this connection is the airtime charge. Since the data connection on the wireline side of the transceiver does not occupy any dedicated bandwidth, a larger number of such data calls can be serviced using the same bandwidth.

In addition, the administration and maintenance of this data service is simplified since there is no need to register with a third-party Integrated Service Provider for purposes of internet access. This access is directly supported by the IP-enabled transceiver unit.

Further, since the data call is not routed through a fixed wireline ISP server, no long-distance charges need apply to the mobile user for the duration of the call. This is true, regardless of the mobility pattern of the mobile computing device. The use of the IP protocol within the wireless infrastructure allows IP packets transmitted by the mobile computing device to find the optimal path to their final destination.

It should be understood that although the preferred embodiment of the present invention refers to a GSM system and standards, nothing herein prevents the application of the present invention to other digital communication systems such as GPRS, CDMA, UMTS, TDMA as well as future to-be-determined digital air-interface standards .

Thus, the present invention provides a method and system for communicating between a first communication unit and a second communication unit. By utilizing IP addresses and sending the signals over an external network, such as the internet, installation and running of communication systems has been simplified. New sites and BTSs can be added to a system by configuring with a unique IP address and connecting to the external network. The connection to the external network can be through an IP gateway connected to various pieces of hardware within a communication site, or can be achieved by connecting a piece of hardware at a communication site to the external network and assigning the piece of hardware a unique IP address. In addition, the communication units that are associated with BTSs or BSC that include IP-enabled LAN interfaces allow the communication units to have direct access to the internet. While this invention has been described in terms of certain examples thereof, it is not intended that it be limited to the above description, but rather only to the extent set forth in the claims that follow.

Claims

1. A method for communicating between a first communication unit and a second communication unit, the first communication unit being in communication with an IP radio, the IP radio being connected to a base transceiver station controller, the base transceiver station controller being connected to a base station controller, the IP radio being coupled to an external network via an IP-enabled local area network (LAN) interface, the method comprising the steps of: transmitting a signal from the first communication unit to the IP radio; receiving the signal at the IP radio; and routing the signal to the second communication unit through the external network via the IP-enabled local area network (LAN) interface.

2. A method for communicating between a first communication unit and a second communication unit in accordance with claim 1, wherein the step of routing the signal to the second communication unit comprises the step of sending the signal from the IP radio to the IP-enabled local area network (LAN) interface.

3. A method for communicating between a first communication unit and a second communication unit in accordance with claim 1, wherein the step of routing the signal to the second communication unit comprises the steps of: sending the signal from the IP radio to the base transceiver station controller; and sending the signal from the base transceiver station controller to the IP-enabled local area network (LAN) interface.

4. A method for communicating between a first communication unit and a second communication unit in accordance with claim 1, wherein the step of routing the signal to the second communication unit comprises the steps of: sending the signal from the IP radio to the base transceiver station controller; sending the signal from the base transceiver station controller to the base station controller; and sending the signal from the base station controller to the IP-enabled local area network (LAN) interface.

5. A method for communicating between a first communication unit and a second communication unit in accordance with claim 1, wherein the step of routing the signal comprises routing a signal that includes a voice portion and a data portion.

6. A method for communicating between a first communication unit and a second communication unit in accordance with claim 5, wherein the step of routing a signal that includes a voice portion and a data portion comprises the step of routing the voice portion prior to routing the data portion.

7. A method for communicating between a first communication unit and a second communication unit in accordance with claim 1, wherein the step of routing is based upon a bituple sent between the first communication unit and the IP radio, the bituple including a communication identification associated with the first communication unit and an IP radio identification associated with the IP radio.

8. A method for communicating between a first communication unit and a second communication unit in accordance with claim 7, further comprising the step of handing off from the IP radio to a second IP radio by changing the IP radio identification in the bituple.

9. A method for communicating between a first communication unit and a second communication unit, comprising: sending a signal from a first communication unit to a Base Transceiver Station (IP radio) , the signal including a destination; and routing, based upon the destination, the signal through an external network.

10. A communication system comprising: a base station controller connected to an external network via an IP-enabled local area network (LAN) interface; and an IP radio coupled to the base station controller via the IP-enabled LAN interface.