KR100188984B1 - Communication across regional entities - Google Patents

Abstract

A method and apparatus for use in a wireless communication system having first and second transcoders 116, 118 organically coupled to first and second transcoders 106, 108, respectively. The system also includes a mobile communication unit requesting the first base station unit and the second base station unit to enter a linked-communication mode. In order to perform link-communication, a transcoder-base station interface link is established between the second base station and the second transcoder. In addition, the second transcoder is configured to operate in a bypass mode such that the second transcoder receives information in the transcoder-base station interface link via a CARE-link associated with a CARE-control-link between the first and second transcoder. Will be relayed. Finally, the first transcoder is made to operate in link-communication mode by relaying information in the CARE-link controlled by the CARE-control-link.

Description

[Name of invention]

Method and apparatus for communication between local entities in communication system

[Related invention]

The present invention relates to the following invention assigned to the assignee of the present invention. Filed on September 17, 1993 and assigned United States Application No. 08 / 123,615, this invention is a method and apparatus for transferring network device operation between network devices invented by Bonta.

[Field of Invention]

The present invention relates to a communication system having a plurality of transcoders, and more particularly to a method and apparatus for communication between local entities in a communication system.

[Background of invention]

The following description relates to the use in a direct sequence code division multiple access (DS-CDMA) communication system. One such DS-CDMA system is described in a communication standard known as mobile station-base station compatibility criteria for IS-95 or dual-mode wideband spread spectrum cellular systems, as well as voice service selection criteria for IS-96 or wideband spread spectrum digital cellular systems. And these are Washington D. city. 20006 Promulgated by the Telecommunications Industries Association (TIA), North Avenue, 20001. However, those skilled in the art are not limited to frequency division multiple access (FDMA) and time division multiple access (TDMA) communication systems, but they can readily extend the principles presented above to other types of communication systems including them. Could be.

As shown in FIG. 2, in the DS-CDMA cellular communication system equipment, different regional transcoder / selection entities are typically limited because the number of communication channels that each transcoder / selection system entity (XC) can support is essentially limited. (Ie, a seam 200 is formed between the cells supported by the XC system A 106 and the XC system B 108 (ie, cell 1 and cell 4). Interchange voice information with voice coding devices (i.e., vocoder) and other communication network devices (e.g., mobile switching center (MSC) or public switched telephone network (PSTN)) that are higher layers of the system layer. In addition, each transcoder / selection entity removes (descarding or combining) voice traffic information frames from being copied (multiple copies to the transcoder / selection entity). Can depend This is because a frame may be transmitted along two or more signal transmission paths through the cellular infrastructure before the frame reaches the transcoder, and each transcoder / selection entity may have bad or missing frames (e.g., (E.g., due to signal transmission blank and burst operations) Finally, each transcoder can duplicate frames for simultaneous transmission to multiple base transceiver stations (BTSs).

One method for handoff across shim 200 is to use hard handoff instead of soft handoff (ie, the soft handoff technique described in IS-95). In hard handoff, the mobile communication unit is instructed to change to a completely new pilot channel set, which means that no diversity selection can be done during the transition from the old transcoder / select entity to the new entity.

However, it is desirable to perform a soft handoff across the shim. Soft handoff (SHO) is maintained in that the source transcoder / selected area entity is smoothly implemented even while multiple operations are being transferred across the shim 200 between target entities. These advantages include providing potential signal receiver gains by adding diversity paths. As will be appreciated by those skilled in the art, the source and target transcoders may be placed in close proximity to one another in a centrally positioned manner, or may be located remotely from one another in a distributedly positioned manner. Whenever a transition occurs, that is, when a source cell is taken out of a soft handoff connection, call ownership is transferred to the controller of the target cell (ie, the link and call operations management device) and one of the associated transcoding / selecting entities. The controller of the target cell that loses ownership is then the source cell controller and makes all subsequent decisions regarding soft handoff until this source cell is removed. Therefore, what is needed is a method of realizing this desired soft handoff across the transcoder shim 200.

[Summary of invention]

These needs and others are practically met as provided methods and apparatus for use in a wireless communication system having first and second base station communication units organically coupled to a first and a second transcoder, respectively. The system also includes a mobile communication unit requesting to enter linked-communication with the first and second base station units. In order to perform link-communication, a transcoder-base station interface link is established between the second base station and the second transcoder. The second transcoder may also relay information in the transcoder-base station interface link via a CARE-link associated with a communication across regional entity (CARE) -control-link between the first and second transcoder. It is configured to operate in the bypass mode. Finally, the first transcoder is configured to operate in the link-communication mode by relaying information in the CARE-link controlled by the CARE-control-link.

[Brief Description of Drawings]

1 is a block diagram illustrating a communication system according to a preferred embodiment with several differently configured transcoder devices in accordance with the present invention.

2 is a diagram of the cellular coverage of a communication system operating in accordance with the preferred embodiment shown in FIG.

3 is a communication flowchart for adding a handoff setup in accordance with the transcoder device configuration of the first embodiment shown in FIG.

4 is a communication flow diagram for eliminating a handoff setup according to the transcoder device configuration of the first embodiment shown in FIG.

Detailed description of the invention

1 illustrates a preferred embodiment of a communication system with several differently configured transcoder devices according to the present invention. The transcoder / selection entity 100 (ie, network device) is the equipment that is a key component in the DS-CDMA system, and the infrastructure vendors themselves install and supply this equipment within the seller's own system architecture as the equipment itself. There is considerable interest in that. The structure shows that the equipment is placed between the BTS 110 and the MSC 112 (e.g., transcoder rack 100, 102, or 104). Between the BTS 110 and the MSC 112 There are configurations in which the transcoder rack is physically arranged, and in another configuration, the transcoder rack is attached to the MSC, and additionally, a plurality of communication links are installed between the transcoder rack and the BTS or the MSC.

The other components in the communication system are interconnected by a mobility manager (MM) 114 and each transcoder XC 106 (collectively referred to as transcoder rack 100). For example, MSC 112 is disposed on one side of XC 106 and a plurality of BTSs 110 and 116 are disposed on the other side of the XC. XC 106 includes a plurality of highway span interfaces, switching functions, shelf controllers, and CDMA unique functions. Multiple interface / controller cards in the XC frame are configured around a time division multiplex (TDM) bus that carries voice and system message calls. The heart of the switch configuration is the 4092-port kiloport switch (KSW). Four KSWs can be spatially switched by kiloport switch expanders (KSWX). KSWX allows transcoder / selector 106 to support sub-rate switching, allowing four 16 kilobits per second (16 kbps) encoded channels to rise to one 64 kbps digital span (DS). Fault management information and intra-frame control messages are delivered via a separate communication application protocol (CAP) bus.

XC 106 includes one or more transcoder cards (XCDR cards). Each XCDR card converts 64 kbps micro-law pulse code modulated (PCM) signals into encoded speech or vice versa (e.g., the encoded speech is preferably IS- Coded according to 96). The XCDR card exchanges encoded voice and PCM with other cards in the transcoder rack 100. That is, encoded voice and PCM input to the KSW for transmission to the appropriate BTS are exchanged with the interface card via the TDM bus (ie backplane). Several key features of the XCDR card include soft handoff (SHO) support (i.e. transcoder selection), voice coding, and message processing for sub-multiplexing control message information into physical layer streams under MM instructions via the CAP interface. There is.

The Supercell Transcoder / Rate Adapter Unit (STRAU) is a modified RAAI rate adaptation format specified in CCITT V.110, as well as the RA2 rate adaptation format specified in CCITT 1.460. Use the International Telecommunications Advisory Committee (CCITT), known as the International Telecommunication Union-Telematic Service (ITU-TS) at 2011, 1211 Place De Nations, Geneva, Switzerland. It outputs 20 ms frames transmitted at a rate of 16 kilobits per second (16 kbps). The modified RA1 rate adaptation format consists of 320 bits, of which 260 bits are for information communication (13 kbps), 21 bits (1.05 kbps) are for control, 35 bits (1.75 kbps) are for frame synchronization, and 4 bits. Is used for time alignment.

In the implementation of DS-CDMA, XCDR outputs 160 bits and adds 11 bits of parity check bits. This leaves a margin of 7.45 kbps out of the total 13 kbps, which at the end rises to 12.2 kbps (without 16 bit-parity from XCDR every 20 ms).

The XCs send these STRUA frames to their respective BTSs via KSW switches and TDM buses, where the switches and buses connect the frames to the appropriate MSI (Multiple Serial Interface Boards). Where MSI provides the T1 link (s) to the BTS. In communication (also referred to as reverse link) originating at the subscriber unit and received at the BTS, the DS-CDMA demodulator of the BTS determines the vocoding rate and sends only the number of voice bits corresponding to the determined vocoding rate in the STRAU format. The T1 link carries 24 DSOs, currently allowing up to 96 16 kbps (compressed voice) links or call channels using RA2 multiplexing. In a DS-CDMA system, frames appearing on T1, moving to the same cell, are generally synchronized in time (except during soft handoff). This is because the cell air interface timing is the same for all channels.

However, there is a need for a method of adjusting the information flow through the XCs 106 and 108 during soft handoff (SHO) on 16 kbps STRAU links at the boundary location or shim 200 (see FIG. 2). This need is addressed by CARE-links as described below. As indicated by dashed line 101 in the figure, these CARE links combine two XCs together so that information can be easily transferred between them. Those skilled in the art will appreciate that these CARE links may be provided through links between XCs leading to one or more MSCs 112 and 122, MM 120, and / or PSTN 124. Could be. If one XCDR is connected to one cell located near the shim 200 (ie, cell 1 associated with BTS 116), another XC 108 connected to a neighbor cell (cell 4 associated with BTS 118). There is a potential situation where there should be one link. If the subscriber unit reports a strong pilot in the cell (ie, cell 4) beyond the shim 200, then the XCs 106 and 108 use the segmented XCDR configuration to control soft handoff beyond their CARE link boundaries. To mediate. As a result, the XCDR can be passed to other resources farther than the subscriber's current location. CARE links use STRAU to frame data for communication between the CAP interface and the XCs for communicating to the parent (MM) entity.

Source XCDR (SXCDR) associated with BTS 116 in XC system 106 terminates the call channel during SHO. The destination XCDR (DXCDR) associated with the BTS 118 in the XC 108 connects the physical link received from its BTS to the SXCDR via the CARE link in bypass mode. At the same time, the DXCDR determines the appropriate time adjustments in case the subscriber unit has to take responsibility if it has moved completely into its cell. The SXCDR transmits voice and adjusts its transcoding window to minimize delay using feedback from the BTS 118 through the STRAU. The selector of the DXCDR monitors the time element information in the STRAU from the BTS 118 and informs the destination transcoder to adjust the window of the destination transcoder. In the CARE link, delay is additionally caused by the path from the other passive XCDR, STRAU to bypass mode. When using the MSC 112 or 122 to establish the STRAU route between the XC 106 and the XC 108, an additional delay may be added to the CARE link. Therefore, some slight BTS span time mismatch must be accommodated. This is preferably done in SXCDR and is automatically controlled by the feedback time alignment protocol. As a delay is added, the result is that SXCDR is ahead of transmission to BTSs.

The MSC can be set up in a three party conference circuit configuration, and the vocoder chip must be programmed to send muted PCM voice frames. The selection function for the two links during SHO is performed in SXCDR. Physically, the subsystems can be connected in a 1.544 kbps link between two XCs 106 and XC 108. Alternatively, the use of MSC (112 or 122) to connect to another XC 108 allows the use of Motorola's proposed A + interface or other communication protocol criteria, i.e., the IS-41 (TIA, 2001, Northwest PA, 2001). Connection may be made on an open interface basis. These connections at the MSC 112 or 122 may be nailed, or a packet scheme may be used.

During the CARE link process, DXCDR monitors STRAU framing while monitoring STRAU information in the STRAU's selector. Data is read from the BTS and immediately written to the SXCDR, while the in-band control bits in the STRAU framing are set to active for the bypass mode. SXCDR maintains active control of the traffic channel, which is done until the MM 114 instructs the SXCDR to transfer control to the DXCDR, which is directed to the subscriber unit alone into the new XC 108 coverage area. Occurs when it is done. Active control means that the XCDR performs the selection, transcoding, and subscriber unit call processing. SXCDR always passes the active control of the traffic channel to DXCDR in the same known state. SXCDR continues to decode the voice, and DXCDT is started for synchronization. The MSC 112 or 122, which is operating in the three-party conference mode, must also know if the MSC's resources are in SHO state to determine blocking.

A typical call flow diagram is shown in FIGS. 3 and 4, which illustrate the messaging required to add or drop a BTS beyond local entities. Those skilled in the art will appreciate that these procedures can also be extended to scenarios involving handoffs to more separate equipment, ie different XCs as well as different MMs.

A communication flow diagram for adding a handoff setup is shown in FIG. The subscriber unit or mobile station (MS) sends a pilot strength measurement message (PSMM) to the BTS, which forwards the PSMM to the SXCDR. If the PSMM indicates that the other BTS pilot signal is greater than a predetermined threshold, then the HO is acknowledged and known to the MM. The MM sets up a CARE link between SXCDR and DXCDR. A generic processor in each transcoder rack identifies the CARE link. Moreover, the MM requests a three-way conference from the MSC or switch (SW) to smooth the call audio quality during handoff. The SW responds to this request. The MM then sends SHO bypass requests to DXCDR on the CARE link. This SHO bypass request is answered by the DXCDR on the CARE link. At the same time or at any time thereafter, the MM also requests a HO channel (ie, a wireless channel) to be assigned by the destination transmitter / receiver (DXCVR) device. The DXCVR responds to communication resource (ie, radio channel) allocation. Once all of this is complete, the MM initiates a handoff at SXCDR. SXCDR not only starts sending subscriber communication information on the CARE link to DXCDR but also monitors the subscriber communication information itself. SXCDR then sends a handoff indication message to the MS. When the MS is acquired by DXCVR, the MS sends a handoff complete message to SXCDR. Once SXCDR receives the handoff complete message, SXCDR notifies the MM that the HO was successful. At this point, the MS is in SHO and is communicating with both SXCDR and DXCDR as well as SXCVR and DXCVR.

4 shows a communication flow diagram for a handoff setup drop. The MS sends a PSMM to SXCDR indicating that the source BTS has a pilot signal strength below a predetermined threshold. If the pilot signal strength remains below a predetermined threshold for a set time interval (at the end of the timer), then the SXCDR sends a drop SHO request to the MM. The MM then sends a vocoder / release control message to SXCDR. The SXCDR then sends an initiation vocoding and communication control message to the DXCDR within the CARE link. This can be achieved by SXCDR with in-band signal transmission in the STRAU to exchange XCDR control in synchronization. DXCDR responds to the control exchange to SXCDR. As a result, the SXCDR notifies the MM that SHO control has been initiated by DXCDR and requests that SXCDR release SHO control from the MM. Moreover, the SXCDR preferably sends a mute audio signal to the SW to smooth out any possible audio holes created by transcoder handoff. The MM then sends a HO indication message to the DXCDR, where the DXCDR forwards the message to the MS. The MS responds to the DXCDR with HO confirmation, and the DXCDR sends a HO success message to the MM. At about the same time, SXCDR releases the radio channel to SXCVR. Moreover, the MM releases the three party conference line in the SW. SW responds to the release of the three-part conference. The MM puts SXCDR in standby mode, which is confirmed by the SXCDR completing the drop of SXCDR from the SHO communication state.

In a variant, the SHO can be extended by connecting a BTS near the transcoder shims in two XC subsystems (ie, XC 108 and 132). Soft handoff between the BTS 126 and the BTS 134 may be accomplished using the CARE signal transmission technique. Typically, it will be necessary to make the handoff between the BTS 126 and the BTS 134 hard handoff (ie, not communicating between transcodes). However, in this manner the BTS 126 and the BTS 134 are Since both are connected to XC-C 132 by dedicated spans 128 and 136, soft handoff may occur between cells. The same CARE signal transmission can be employed with slightly different physical link schemes. This approach minimizes the bypass mode bandwidth required for CARE signal transmission in exchange for having extra dedicated spans 128 and 130 in multiple transcoders per BTS.

The principles described herein can be summarized as follows. The wireless communication system (shown in FIG. 1) preferably includes first and second transcoders 106, 108 organically coupled to each of the first and second base station communication units 116, 118. In addition, a mobile communication unit (not shown) operating within the system requests the first and second base station communication units 116, 118 to enter a soft handoff mode. The method provides a method for performing a soft handoff comprising establishing a transcoder-base station interface link between a second base station 118 and a second transcoder 108. In addition, the second transcoder 108 is configured to operate in the bypass mode, such that the second transcoder 108 is a CARE-link associated with a CARE-control-link between the first and second transcoders 106 and 108. This will relay the information on the transcoder-base station interface link. In the present embodiment, the second transcoder 108 synchronizes the CARE-link with the transcoder-base station interface link so that communication between the two links can be relayed with little delay. Finally, the first transcoder 106 is configured such that the first transcoder 106 operates in link-communication mode by relaying information in the CARE-link controlled by the CARE-control-link. In a variant, the second transcoder 108 relays the information in the transcoder-base station interface link via the CARE-link and on the CARE-control-link between the first transcoder 106 and the second transcoder 108. Can operate in bypass mode to monitor control messages.

In response to determining that communication with the first base station 116 must be removed to achieve a transcoder operational handoff (ie, SHO), the second transcoder 108 must take over communication with the mobile communication unit. Control information indicating that the data is transmitted to the second transcoder 108. The second transcoder 108 monitors the communication link to obtain subsequent control information. The particular communication link monitored can be a CARE-link, a CARE-control-link, or a transcoder-base station interface link. Finally, in response to the second transcoder 108 receiving control information on the monitored communication link, the second transcoder 108 has control over communication with the mobile communication unit. This step of controlling configures the first transcoder 106 to operate in the bypass mode, such that the first transcoder 106 is over the CARE-link by the first base station 116 and the first transcoder 106. In addition to relaying information on the inter-transcoder-base station interface link, it may also include setting up the first transcoder 106 to monitor the CARE-control-link to obtain subsequent control signals. Such a monitor may consist of detecting a change in control information content or waiting for a timeout event. In addition, the step of having control may further include acknowledging via the CARE-control-link that the second transcoder 108 has control of the communication with the mobile communication unit. At the same time, the first transcoder 106 can be released from communication with the mobile communication unit.

In a variant, the second transcoder 108 switches the transcoding operation to another transcoder capable of encoding and decoding speech information.

Alternatively, in response to determining that communication with the second base station 116 is to be removed, control information indicating that the second transcoder 108 should terminate communication with the mobile communication unit is transmitted. Transcoder operation handoff can be stopped by delivering to the coder 108. The second transcoder 108 also monitors the communication link to obtain control information. The particular link monitored may be a CARE-link, a CARE-control-link, or a transcoder-base station interface link. Finally, in response to the second transcoder 108 receiving control information on the monitored communication link, the second transcoder 108 is released from communication with the mobile communication unit.

Those skilled in the art, these steps of transferring transcoder operations are via a CARE-link and a CARE-control-link that each include a logical connection between the first transcoder 106 and the second transcoder 108, respectively. Will be achieved. The logical connection may be formed by operation coupling between at least two of the following system entities, wherein the system entities include a first transcoder 106, a second transcoder 108, a first mobility manager 114, and a second. Mobility manager 120, first base station controller 116, second base station controller 118, first communication network switch 112, second communication network number location 122, location register, and public switched telephone network 124 ) Is included.

In addition, as will be appreciated by those skilled in the art, the SHO is organically coupled to pulse code modulation information signals associated with each of the first and second transcoders 106 and 108 as well as one or more communication network switches 112. It may also include enabling a three-way conference line. In addition to this enabling step, an audio mute should be included in the third party conference line during the call handoff so that spurious audio noises in the call can be reduced.

Furthermore, as will be appreciated by those skilled in the art, the link communication mode of handoff between delay entities has been described in detail, but the principles included herein are not limited to the scope and spirit of the present invention, and may be used for diversity combination and communication link encryption. It can be easily applied to other link communications including encryption.

While the invention has been described and illustrated with some detail, the embodiments disclosed herein are merely exemplary and numerous modifications in construction and combination of components and steps are intended to deviate from the spirit and scope of the invention as claimed. It will be appreciated that those skilled in the art can do this without. For example, descriptions of network device operations have been made in the context of transcoder handoff operation. However, those skilled in the art will appreciate that what is presented in the present invention can be readily applied to use in other forms of network device operation, such as diversity combinations and communication link encryption processing. The source and target network devices may also be devices other than transcoders, such as mobility managers, base station controllers, communication network switches, or location registers. Finally, other wireless communication channels may be used instead of electronic data buses, wired, fiber optic links, satellite links, or other forms of communication channels.

Claims (2)

First and second transcoders for converting modulated data to encoded speech or for converting encoded speech to modulated data, a first organically coupled to the first and second transcoder, respectively. And a second base station communication unit and a mobile communication unit requesting to enter a linked-communication mode with the first and second base station communication units. (a) establishing a base station communication link between the second base station communication unit and the second transcoder; (b) bypassing the second transcoder mode, in which the second transcoder communicates information received from the second base station communication unit via the base station communication link (CARE); regional entities)-relaying to the first transcoder via a CARE link associated with a control-link; (c) configuring the first transcoder to operate in a hink-communication mode by relaying information in the CARE-link controlled by the CARE-control-link; (d) in response to determining that communication with the first base station communication unit should be removed, conveying control information to the second transcoder indicating that the second transcoder should take over communication with the mobile communication unit. Doing; (e) monitoring a communication link to obtain control information at the second transcoder side, the communication link being selected from the group consisting of the CARE-link, the CARE-control-link, and the base station communication link; And (f) in response to the second transcoder receiving control information on the communication link, placing the second transcoder in a handoff mode, the handoff mode being one as well as the first and second transcoders, respectively. Enabling a three party conference circuit organically coupled to the pulse code modulation information signals associated with the communication network switch above, thereby operating at the second transcoder side. Controlling communication with the mobile communication unit. A method of releasing soft handoff communication between a mobile unit and at least first and second base stations in a wireless communication system, the wireless communication system supporting a first transcoder supporting the first base station and the second base station. A second transcoder, wherein the first and second transcoders convert the modulated data into encoded speech or the encoded speech into modulated data, the first transcoder side Receiving a signal strength message from the mobile unit at; The second transcoder side with respect to the second transcoder via a low delay communication link between the first transcoder and the second transcoder from the first transcoder to the second transcoder. Transmitting a message instructing to initiate control of the vocoder at; Transmitting a handoff indication message from the second transcoder to the mobile unit via the second base station; Releasing control of the bot to the first transcoder; And releasing a radio channel between the first base station and the mobile unit.