HK1073959B - Method and apparatus for channel management for point-to-multipoint services in a communication system - Google Patents

Description

Method and apparatus for channel management for point-to-multipoint services in a communication system

The copending provisional application No.60/279970 filed on 28.3.2001 entitled "METHOD AND APPARATUS FOR GROUOP CALLS USE DEDICATED AND COMMUNICANNELLIN WIRENESS NETWORKS" is claimed as a priority.

Technical Field

The present invention relates to a point-to-multipoint service in a wired or wireless communication system. In particular, the present invention relates to a method and apparatus for channel management of such point-to-multipoint services in a communication system.

Background

Communication systems have evolved to propagate information signals from an origination station to a physically distinct destination station. In transmitting an information signal from an origination station over a communication channel, the information signal is first converted into a form suitable for efficient transmission over the communication channel. The conversion or modulation of the information signal involves changing the parameters of the carrier in such a way that the information signal limits the spectrum of the resulting modulated carrier within the bandwidth of the communication channel. At the destination station, the original signal is reproduced from a modulated carrier wave received over the communication channel. This recurrence is typically achieved by using the inverse of the modulation employed by the origination station.

Modulation also facilitates multiple access, i.e., simultaneous transmission and/or reception, of several signals over a common communication channel. Multiple-access communication systems often include multiple remote user terminals that require intermittent service for relatively short periods rather than continuous access to a common communication channel. Several multiple access techniques are known, such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and modulation multiple Access (AM). Another type of multiple ACCESS technique IS Code Division Multiple ACCESS (CDMA) SPREAD spectrum SYSTEMs that conform to the "TIA/EIA (IS-95 mobile station-base station compatibility standard for dual mode wideband SPREAD CELLULAR SYSTEMs" (hereinafter the IS-95 standard.) applications of CDMA techniques in multiple ACCESS COMMUNICATION SYSTEMs are disclosed in U.S. patent No. 4,901,307, entitled "SPREAD spectrum COMMUNICATION SYSTEM US ING SATELLITE OR tertiary SYSTEMs," and U.S. patent No.5,103,459, entitled "SYSTEM AND METHOD for COMMUNICATION SYSTEM a CDMA CELLULAR TELEPHONE SYSTEM," both assigned to the assignee of the present invention.

Multiple-access communication systems may be wireless or wired and may carry voice and/or data. An example of a voice and data-bearing communication system IS one that provides for the transmission of voice and data over a communication channel in accordance with the IS-95 standard. One METHOD OF transmitting DATA in fixed size code channel frames is described in U.S. patent No.5,504,773 entitled "METHOD AND APPARATUS FOR the TRANSMISSION OF DATA FOR TRANSMISSION" (assigned to the assignee OF the present invention). According to the IS-95 standard, data or speech IS divided into code channel frames, 20ms wide, with data rates up to 14.4 Kbps. Further examples of carrying voice and data include communication systems compliant with the "3 rd generation partnership project" (3GPP), which is accommodated in a set of documents: and (4) file Nos. 3G TS 252111, 3G TS25212, 3G TS25213, and 3G TS 25214(W-CDMA standard), or "TR-45.5 physical layer Standard for CDMA 2000 Spectrum spread systems" (IS-2000 standard).

In a multiple access communication system, communication between users is conducted through one or more base stations. A 1 st user of one subscriber station communicates to a 2 nd user of a 2 nd subscriber station by transmitting data on the reverse link to the base station. The base station receives the data and routes the data to another base station. The data is transmitted to the 2 nd subscriber station on the forward link of the same base station or another base station. Communication can likewise take place between a 1 st subscriber on a mobile subscriber station and a 2 nd subscriber station on a land communication station. The base station receives data from users on the reverse link and routes the data to the 2 nd user through the Public Switched Telephone Network (PSTN).

The wireless communication service described above is an example of a point-to-point communication service. In contrast, a point-to-multipoint service is a service that distributes information provided by an information source to a plurality of users. The basic point-to-multipoint model includes a group of users at subscriber stations that receive information from one or more information sources over a wired or wireless network. In point-to-multipoint services, the source fixedly determines the content of information such as news, movies, sports events, etc., and the user generally does not communicate back. To conserve resources, each subscriber station (member subscriber station) that generally refers to a point-to-multipoint service monitors a shared channel modulated by information. Such a point-to-multipoint service is also called broadcasting or multicasting, and examples of general applications thereof include TV broadcasting, radio broadcasting, and the like. On the other hand, the information sources are users, members of the group, which send information intended for the remaining group members. If the user wants to speak, he presses the talk button (PTT). Typically, a user's voice is routed from the subscriber station to the network on a dedicated reverse link channel. The network then transmits the speaker's voice over the forward link common channel. As with point-to-point communication systems, such communication systems provide access to the system by landline and wireless subscriber stations. Such a point-to-multipoint service is also called a group service. Examples of group service communication applications are dispatch services such as local police radio systems, taxi dispatch systems, federal intelligence bureau and stealth service operations, and general military communication systems.

The point-to-multipoint service communication systems described above are typically highly dedicated communication systems. With recent advances in wireless cellular telephone systems, there is an interest in utilizing existing infrastructure, primarily point-to-point cellular systems, for point-to-multipoint services. As used herein, the term "cellular" system encompasses systems that operate at both cellular and Personal Communication System (PCS) frequencies.

As discussed, to conserve resources, point-to-multipoint services typically rely on providing a common forward link channel to be monitored by all member users. In contrast, wireless cellular telephone systems allocate dedicated forward and reverse link channels between base stations or sectors whose coverage areas contain users who desire to communicate. Because of the limited number of such dedicated forward and reverse link channels that can be supported by the wireless cellular telephone system, there is a limited number of members that can join the point-to-multipoint service provided over the dedicated forward and reverse link channels. There is also a need to enable both group and telephony services in a wireless cellular telephone system. There is therefore a need in the art for methods and apparatus for providing such channel management of group services and telephony services using the infrastructure of a wireless cellular telephone system.

Disclosure of Invention

In one aspect of the present invention, the above requirements are addressed by channel management in a communication system, comprising assigning a common forward channel to each subscriber station belonging to a group during activity; and assigns a forward channel to each subscriber station belonging to a group during the silence period.

In another aspect of the present invention, the above requirements are addressed by channel management in a communication system, comprising assigning a dedicated reverse channel to each subscriber station belonging to a group during an activity period; modulating the dedicated reverse channel by active subscriber station user data and control data belonging to the group; and modulating the dedicated reverse channel with control data by passive subscriber stations belonging to the group.

In yet another aspect of the present invention, the above requirement is illustrated by subscriber stations belonging to a group transmitting a request to modulate a reverse link channel; and receiving a response to the request to transmit over a forward link channel monitored by the subscriber station. All reverse link channels and the forward link channel monitored by the subscriber station depend on the point-to-multipoint service activity such as silence and the same state of activity. The response may include the reverse link channel assignment and explicit transmit permission.

In yet another aspect of the present invention, the above requirements are addressed by assigning different forward links to be monitored and reverse links to be used by member mobile stations based on the time of point-to-multipoint service activity, such as silence and activity.

Drawings

Fig. 1 is a conceptual diagram illustrating a point-to-multipoint service communication system.

Detailed description of the invention

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Although the best mode embodiment is included herein. Embodiments described as "exemplary" are not necessarily to be construed as preferred or advantageous over other embodiments.

The term "point-to-point communication" refers herein to communication between two subscriber stations over a dedicated forward communication channel and a dedicated reverse communication channel.

The term "point-to-multipoint communication service" refers herein to a communication in which a plurality of subscriber stations are receiving communications from (typically) a source. Such services may include, for example: packet services, where the source is a subscriber station; a broadcast service, wherein the source is a central station; or a multicast service in which the recipient includes a subset of a plurality of subscriber stations.

The term "access network" herein refers to a collection of base stations and a controller of one or more base stations. An access network transports data between a plurality of subscriber stations. The access network may also be connected to additional networks outside the access network, such as a public intranet or a network, through which data may be transferred between each access terminal and this extranet.

The term "base station" herein refers to the hardware with which subscriber stations communicate. "cell" refers to either a hardware or a geographic coverage area, depending on the context in which the term is used. A "sector" is a portion of a cell. The principles described with respect to base stations/cells can be extended to sectors as sectors have the properties of cells.

The term "subscriber station" herein refers to the hardware with which the access network communicates. The subscriber station may be mobile or stationary. A subscriber station may be any data device that communicates through a wireless channel or through a wired channel, such as using fiber optic or coaxial cables, and may be any of several devices including but not limited to PC cards, compact flash, external or internal modems, or wireless or wireline telephones. A subscriber station in the process of establishing an active traffic connection with a base station is referred to as a connected state.

The term "physical channel" herein refers to a communication route over which a signal described by modulation characteristics and coding propagates.

The term "logical channel" refers herein to the routing of communications in the protocol layer of a base station or subscriber station.

The term "communication channel/link" herein refers to a physical channel or a logical channel by context.

The term "reverse channel/link" refers herein to a communication channel/link through which a subscriber station transmits signals to a base station.

The term "forward channel/link" refers herein to a communication channel/link through which a base station transmits signals to a subscriber station.

The term "soft handoff" is used herein to refer to communication between a subscriber station and two or more sectors, where each sector belongs to a different cell. Reverse link communications are received by two sectors and forward link communications are simultaneously carried on the forward links of two or more sectors.

The term "softer handoff" refers herein to communication between a subscriber station and two or more sectors, where each sector belongs to the same cell. Reverse link communications are received by two sectors and forward link communications are simultaneously carried on a forward link of one of the two or more sectors.

The term "shrinking" here means that the 1 st information content of the 1 st size is replaced by the 2 nd information content of the 1 st size.

The term "dedicated channel" herein refers to a channel modulated with information that allocates individual subscriber stations.

The term "common channel" herein refers to a channel modulated with information that is common among all subscriber stations.

The term "user data" or "payload" refers herein to data other than control data.

The term "control data" herein refers to data that enables operation of entities in a communication system. Control data includes, for example, call hold signaling, diagnostic and reporting information, etc.

Fig. 1 illustrates an overview of a communication system 100 capable of providing point-to-point services in accordance with the present invention. For clarity, the following description shows a packet service, however, those skilled in the art understand how to apply the disclosed concepts to a point-to-multipoint service. The (call) group is determined by the members of the group, including users of the group talking to each other often enough to establish the call group. The group of calls is said to be in a dormant state when no members or members are idle or active, i.e., all members or non-participating calls constitute a shutdown of their subscriber stations. The call group is in an idle state when at least one member joins the group. When one of the at least 2 members initiates a group call, the call group is active. Group calls are divided into active and silent periods. The group call is active when there is propagation between members without long idle periods. When no member transmits any traffic for a long idle period, the group call is a silent period.

During activity, a group of users at a subscriber station, such as subscriber station 102(1), notifies other groups of users at subscriber stations 102(2) through 102(5) of user information (voice or data) via an access network including base station 104 and controller 110. For simplicity, the term "member subscriber station" is used herein to refer to "group users on a subscriber station," unless otherwise specified. Base station 104 is connected to controller 110 through backhaul 112. The term "backhaul" herein refers to the communication link between the controller and the base station. Backhaul 112 may be implemented with a variety of connection types including, for example, microwave or wired E1 or T1, fiber optics, and other connection types as known to those skilled in the art. Controller 110 is coupled to interface unit 114, which couples communication system 100 to other services (not shown) such as a Public Switched Telephone Network (PSTN), a Packet Data Serving Node (PDSN), and other services known to those of ordinary skill in the art.

When a member user group, such as user group 102(1), wants to send user data to that group over the reverse link, the member user group needs to request assignment of the reverse link and permission to send. A control unit located in a single sector, a base station containing a sector, a controller, or any other unit containing an access network is responsible for channel allocation. The assignment is then provided to the member subscriber stations over the forward link channel monitored by the subscriber stations. The reverse link is divided into reverse link channels. Once a member subscriber station 102(1) is assigned a reverse link channel 108(1), subscriber station 102(1) may send information to base station 104 (1). Such a sending member subscriber station is referred to as an active member or speaker. Base station 104(1) routes the received information to base stations 104(2) and 104(3) and sends the received information on forward link shared channel 106(1) to subscriber station 102 (2). Base stations 104(2) and 10493 send information for the route on forward link common channels 106(2) and 106 (3). To receive information from the active member subscriber stations 102(1), all of the member subscriber stations assigned to the active group, i.e., user groups 102(1) through 102(5), monitor the forward link common channel 106 of their individual base stations 104 during the active group call. Generally, the forward link common channels 106(1), 106(2), and 106(3) allocated by the base stations 104(1), 104(2), and 104(3) are different from each other. However, to improve reception by member subscriber stations 102 located in overlapping coverage areas, forward link shared channel 106 may be transmitted synchronously by more than one sector or base station 104. A METHOD for improved reception of the forward link common shared channel IN overlapping coverage areas is disclosed IN co-pending application No.09/333,607 entitled "METHOD AND SYSTEM A handover IN a broadcast communication SYSTEM" (filed 8/20 2001) (assigned to the assignee of the present invention). Those skilled in the art recognize that a base station serving an area may be sectorized. Thus, the terms sector and base station are used interchangeably unless specifically stated otherwise.

In one embodiment, the forward link shared channel 106 is controlled by user information intended for the member subscriber stations and control information, such as signaling information, power control information, and other types of information known to those skilled in the art as necessary for the overall operation of the communication system. However, the limited capacity of the forward link shared channel prevents modulation of both call information and call maintenance information. Thus, in another embodiment, only user information is sent on the forward link shared channel 106 and control information may be modulated on an additional forward link channel (hereinafter referred to as a control/signaling forward link channel). Here, each member user group 102 must monitor the control/signaling forward link channel in addition to the forward link shared channel. Such control/signaling channels may be dedicated channels or shared channels.

The silence period begins when the active period ends, i.e., member subscriber stations 102(1) end communication and no other member subscriber stations 102 begin communication for the decision period 1. To minimize the waste of capacity, the member subscriber station 102 stops monitoring the forward link shared channel 106, as well as the control/signaling forward link (if any), and begins monitoring the determined forward link channel, thus transitioning to a dormant state. In one embodiment, the transmission of the forward link shared channel 106 may be stopped. The term dormant state is used herein to refer to a state where the transition from this member subscriber station 102 to forward link common channel monitoring is made according to a predetermined procedure. Such a predetermined procedure may be implemented as a state machine. After a decision period of no group communication activity, the member subscriber stations 102 transition from the dormant state to the idle state. In the idle state, member subscriber stations 102 monitor the determined forward link channel, but the transition to forward link shared channel monitoring is performed according to a predetermined procedure that variously transitions from the dormant state to the predetermined procedure for forward link channel monitoring. In addition, if a member subscriber station 102 knows that a group call is ended, the member subscriber station 102 may transition directly to an idle state. In another embodiment, the member users 102 are instructed by the control body through the base station 104 to turn to the appropriate state.

When the silence period ends and the active period begins, the member subscriber stations 102 transition from the dormant or idle state back to the forward link shared channel 106. The member subscriber stations 102 are informed of the start of the active period by a channel message sent through the base station 104 in a dormant or idle state on the forward link channel monitored by the member subscriber stations 102.

A request for the above concept of a communication system IS explained in detail below in the IS-2000 standard. Although the following description will be made with respect to channels employing a communication system defined in accordance with the IS-2000 standard. Those skilled in the art will be able to extend the concepts described above to channels of communication systems in accordance with other standards.

Forward link channel allocation

To maximize capacity and minimize power consumption while allowing multiple user receiving user communications (voice or data), members of the active set are assigned their single sector forward link shared channel when the active set call is providing member subscriber stations with information that allows the member subscriber stations to receive data modulated on the forward link shared channel. In one embodiment, in a communication system in accordance with the IS-2000 standard, the forward link shared channel comprises a forward supplemental channel (F-SCH) that IS modulated by both user data and control data and shared by member subscriber stations in the sector's coverage area. When a member subscriber station joins the active set, the controller allocates the member subscriber station to monitor (demodulate) the shared F-SCH for a limited or unlimited period via the appropriate sector. This allocation is accomplished by transmitting an allocation message over the channel which subscriber station is monitoring while in an idle or dormant state. The common F-SCH may operate in a fixed rate mode for simplicity or a variable rate mode for greater flexibility. The term variable mode is used herein to refer to changing within a consistent agreed set of data rates without notification.

Once the member subscriber stations are monitoring the F-SCH, control data necessary to maintain the call, such as pilot strength measurement messages, handoff direction messages, handoff complete messages, and other messages known to those skilled in the art, as well as control data related to the group call, may be transmitted on the F-SCH. The group call related messages include, for example, the start and end of the group call, requests and grants for transmission rights, and other messages known to those skilled in the art. Since the F-SCH is a shared channel, appropriate member subscriber station access information must be employed to enable the member subscriber stations to distinguish the common information for all member subscriber stations from the dedicated information for a particular member subscriber station. The overhead of this control data and member subscriber station access adversely affects the user data load capacity of the F-SCH. Therefore, the control data message is either loaded on the control/signaling forward link channel.

In one embodiment, the overall control/signaling forward link channel, including the forward dedicated control channel (F-SCH), IS sector allocated to each individual member subscriber station in a communication system according to the IS-2000 standard. The F-DCCH may be modulated with, among other control data, reverse link power control commands that control the transmit power level transmitted by the member subscriber stations on the reverse link channel. The power control command includes puncturing into a forward power control subchannel (F-PCSCH) of the F-DCCH. The term puncturing refers herein to sending reverse link power control commands instead of F-DCCH commands. When there is no signaling load on the F-DCCH, less power and capacity is consumed when only the F-DCCH is transmitted. Other power control methods in point-to-multipoint service communication systems are disclosed in the following patents: pending application No. "POWER CONTROL POINT-TO-MULTIPOINT SERVICES PROVIDED IN COMMUNICATION STSTSTSTSTSTSTSTSTSMS", filed 3, 28/2002 and intended for assignment TO the assignee of the present inventors.

Alternatively, in a communication system according to the IS-2000 standard, individual member subscriber stations are sector-allocated to control entity control/signaling forward link channels, including a forward common control channel (F-CCCH), a forward broadcast channel (F-BCCH), or a combination of F-CCCH and F-BCCH. Thus, the signaling messages for the member subscriber stations are modulated on the F-CCCH/F-BCCH. In addition, reverse link power control commands that control the transmit power level transmitted by the member subscriber station reverse link channel may be modulated on the forward common power control channel (F-CPCCH). Less power and capacity is consumed when the F-CPCCH is transmitted without signaling on the F-CCCH/F-BCCH. The next application of the CPCCH is disclosed in the above-referenced patent, pending application No. xxx x entitled "POWER CONTROL FOR POINT-TO-MULTIPOINT SERVICES PROVIDED DIN COMMUNICATION SYSTEMS", filed 3, 28.2002 and assigned TO the assignee of the present invention.

The member subscriber stations may inform the transmitting sector about the quality of service (QoS). Thus, in one embodiment, when the common information for receiving the modulated forward link shared channel is in error, the member subscriber stations may notify the transmitting sector of the error and retransmit the information. In a communication system according to IS-2000, a reverse enhanced access channel (R-EACH) may be used for QoS reporting. In one embodiment, the retransmission occurs on a forward link shared channel. In another embodiment, retransmission occurs on a control/channel forward link channel assigned to the member subscriber stations, such as F-DCCH, F-CCCH, F-BCCH. This is convenient when the delay and delay variation caused by the retransmission are tolerable for the application. Details regarding retransmissions are disclosed in the following patents: pending application No.09/989,347 entitled "SYSTEM AND METHOD FOR FRAME RE-TRANSMISSION IN ABROADCAST COMMUNICATION STSTSTSTTEM", filed 2001, 7/2/2001, assigned to the assignee of the present invention.

In another embodiment, the forward link shared channel includes: F-CCCH, F-BCCH or a combination of F-CCCH and F-BCCH. Member users may share the F-CCCh and F-BCCH for group calls while non-member subscriber stations monitor the F-CCCh and F-BCCH for pages. The F-CCCH and F-BCCH for group calls can simply operate in a fixed rate mode or flexibly in a variable rate mode. Since the F-CCCH and F-BCCH are common channels, appropriate subscriber station access information must be employed so that the subscriber station can distinguish common information intended for member subscriber stations from information specific to individual subscriber stations.

To avoid access overhead, the F-CCCH and F-BCCH may be separated in one embodiment such that some of the F-CCCH and F-BCCH in a sector are allocated as forward link common channels for member subscriber stations for point-to-multipoint service and the remaining F-CCCH and F-BCCH are allocated for paging dedicated to non-member subscriber stations.

As discussed, the channel messages and overhead accessed by the subscriber station adversely affect the traffic capacity of the forward link shared channel, so signaling messages are either carried on the control/channel forward link channel. Thus, when some of the F-CCCHs and F-BCCHs in a sector or base station are allocated as forward link shared channels for point-to-multipoint services, the additional F-CCCH and its associated forward quick paging channel (F-QPCH) may be utilized for paging and the additional F-BCCH for point-to-multipoint service signaling. The member subscriber stations continue to monitor the F-CCCH and F-BCCH and the signaling F-BCCH assigned to the group as the forward link shared channel. In addition, the application of allocating each member subscriber station to monitor the time slots on the F-QPCH to determine whether the F-CCCH associated with the F-QPCH needs to be monitored IS well described in IS-2000, as IS well known to those of ordinary skill in the art.

When the active member subscriber station is in communication with the base station, in one embodiment, reverse link power commands are transmitted on the forward link shared channel, i.e., the F-CCCH/F-BCCH. In another embodiment, reverse link power commands for both member subscriber stations and non-member subscriber stations are modulated onto the F-PCSCH. To properly interpret the reverse link power commands, each individual subscriber station monitors a different substream of power control commands on the F-PCSCH assigned to the subscriber station. Or some F-PCSCH may be assigned to member subscriber stations in a sector or base station while F-CPCCH may be assigned to non-member subscriber stations. Also, each individual subscriber station is assigned to monitor a different substream of power control commands on the assigned F-PCSCH. The use of F-CPCCH is disclosed IN the above-mentioned co-pending application No. xxx x entitled "METHOD AND APPARATUS FOR A POWER CONTROL IN A POINT-TO-MULTIPOINT SERVICES INA COMMUNICATION SYSTEM", filed 3, 28, 2002 and assigned TO the assignee of the present inventors.

The member subscriber stations may inform the transmitting sector about the quality of service (QoS). Thus, in one embodiment, when a member subscriber station receives common information for the modulated forward link common channel, F-CCCH or F-BCCH, in error, the member subscriber station may inform the transmitting sector of the error using the reverse enhanced access channel (R-EACH) and retransmit the information. Retransmissions occur on the group call F-CCCH or F-BCCH. Retransmissions are convenient when the time delay and retransmissions cause delay variations that can be tolerated in the application. The details of retransmission are disclosed IN the aforementioned No.009/989,347 filed on 7/2/2001 entitled "SYSTEM AND METHOD FOR FRAMERE-TRANSMISSION IN A BROADCAST COMMUNICATION SYSTEM" assigned to the assignee of the present invention.

Reverse link channel allocation

As described above, typically only one member subscriber station transmits on the reverse link at a time. Thus, while passive member subscriber stations do not transmit user data onto the reverse link of any sector, the passive member subscriber stations need to use the reverse link to inform sector information needed for call maintenance, such as: handover messages, power control, and other information known to those skilled in the art. The term passive here refers to member subscriber stations monitoring the common channel of the forward link and any control/signaling required for a group call on the forward link channel but not transmitting user data on the reverse link channel. In addition, the passive member subscriber stations may wish to be notified of certain data, and therefore require equipment to request reverse traffic channel assignment. The passive member subscriber station may require an assigned reverse link channel.

According to one embodiment, the control entity assigns a reverse dedicated channel to each individual member subscriber station via a sector, which in a communication system according to the IS-2000 standard includes a reverse dedicated control channel (R-DCCH) joining an active set. The passive member subscriber stations use the R-DCCH for transmitting control data for regular calls (e.g., reports of forward link pilots) and transmit control data related to group calls (e.g., quality measurement reports of forward link broadcast channels, requests for reverse link traffic channel assignments). The active member subscriber stations also use the R-DCCH to transmit user data. When transmitting the R-DCCH, the member subscriber station also transmits a reverse pilot channel (R-PICH) and a reverse power control subchannel (R-PCSCH). The R-PCSCH carries feedback on the quality measurement of the forward link shared channel.

Since the R-DCCH is modulated only with control data, there is a period during which such information is not required to be transmitted. The passive member subscriber station may stop transmitting the R-DCCH and transmit only the R-PICH multiplexed with the R-PCSCH. This mode of operation IS illustrated in the IS-2000 standard.

The reduction in power and capacity consumption may be further achieved by gating if the period of inactivity exceeds a predetermined period. The term gating here refers to the excitation of the R-PICH/R-PCSCH transmission only within a predetermined Power Control Group (PCG). Furthermore, as with the frequency drop in sector power measurements, the data rate of the corresponding substream on the F-CPCCH carrying the reverse control power commands is reduced because the requirements for sophisticated reverse link power control become less important. The rate reduction of the F-CPCCH can be achieved by allocating the gated member subscriber stations to lower rate substreams or by sharing higher rate substreams by multiple gated member subscriber stations.

Furthermore, if no power control commands need to be transmitted, the transmission of the R-PCSCH can be suspended according to the IS-2000 standard, and he only needs to transmit the R-PICH from the subscriber station, i.e., the R-PICM continues to transmit without the multiplexed R-PCSCH. Further, the transmission of the R-PICH/R-PCSCH can be completely stopped. This results in stopping the substreams on the corresponding F-CPCCH.

And a combination of the two approaches may be used. In this method, the member subscriber station starts gated R-PICH/R-PCSCH transmission after the 1 st inactive period and stops R-PICH/R-PCSCH transmission after the 2 nd inactive period. The data rate of the corresponding F-CPCCH is reduced accordingly.

If the member subscriber station requires transmission of a control data signaling message during gated or stop mode on the R-DCCH, the transmission of the 1 st signaling message ends the gating, i.e., the R-PICH, R-PCSCH, and R-DCCH are continuously activated during the signaling message. Once the signaling message has been sent, the subscriber station reverts to gated or stopped mode as above. Also, to assist the sector in acquiring subscriber station signals, the R-PICH can be activated as a preamble before the R-DCCH message at an elevated power level.

In another embodiment, only active subscriber station-specific reverse link channels, such as R-DCCHs, are allocated. A passive subscriber station-specific reverse link channel is not allocated. And the passive member subscriber stations use the reverse enhanced access channel R-EACH for reverse link signaling when needed, using basic access, memory access, and power control access. Basic access, memory access, and power control access are defined in the IS-2000 standard and are well known to those skilled in the art.

According to the basic access mode, the member subscriber station randomly selects an R-EACH and transmits a header on the R-PICH with increased power, and then transmits a message on the R-EACH. The member subscriber stations then monitor the forward link shared information for acknowledgement and begin transmitting on the R-EACH after receiving the acknowledgement.

According to the memory access mode, the member subscriber station randomly selects the R-EACH and transmits a short header to the sector over the R-EACH to reduce the likelihood of collisions with other access attempts over the R-EACH, which collisions may result in loss of access attempts. The sector transmits an Early Acknowledgement Channel Assignment Message (EACAM) on a forward common assignment channel (F-CACH) to assign a reverse common control channel (R-CCCH) to the member subscriber stations. The member subscriber station then monitors the forward link shared channel for EACAM and starts transmitting on the R-CCCH after receiving EACAM.

In another embodiment, the member subscriber station transmits in a Power Control Access Mode (PCAM) over the R-EACH. In PCAM, the access procedure is similar to memory access and the transmission over the R-EACH is power controlled by allocating power control bits transmitted by the base station upon reception of the R-EACH on the forward common power control channel (F-CPCCH).

Send to the group

When a member subscriber station wants to transmit voice or data to a group, the member subscriber station must wait for a reverse channel to be allocated and get access to the grant of the transmission.

As described above, in one embodiment, each member subscriber station is assigned a reverse link channel for transmitting control data, such as R-DCCH, based upon participation in the active set. When the group activity is over, the member subscriber stations do not need to transmit control data, so after a predetermined period of group call inactivity, the member subscriber stations release the reverse link channel and begin monitoring the different reverse link channels for communication system access. In one embodiment, the member subscriber stations monitor the reverse access information (R-ACH) or reverse enhanced access channel (R-EACH). Control data signaling messages are then sent from the member subscriber stations to the sector over the R-DCCH when the member subscriber stations in the active call are not inactive for more than a predetermined period of time to require transmission of user data. If the member subscriber station has released the R-DCCH, the member subscriber station transmits a control data signaling message on the R-ACH or R-EACH.

In an embodiment, the control data signaling message is a request to allow transmission. Upon receiving the request, the sector sends a grant for transmission over a forward link channel monitored by the member subscriber group. As described above, when the silent period exceeds a predetermined period, the member subscriber station stops monitoring the forward link shared channel and controls/signals the forward link channel (if monitored) and starts monitoring the decided forward link channel, thereby shifting to the dormant state. Thus, if there is a recent group activity that does not exceed a predetermined period of inactivity, the member subscriber station is monitoring the forward link shared channel or the control/signaling forward link channel; a grant is then issued on the forward link shared channel or control/signaling forward link channel. If the member subscriber station has released the forward link shared channel and the control/signaling forward link channel, a grant is issued on the forward link channel monitored by the member subscriber station. In this case, signaling messages must be sent to all member subscriber stations to begin monitoring the forward link shared channel, and control/signaling forward channels (if used), in their sectors. Upon receipt of the grant to use the R-DCCH by a member subscriber station, reverse link transmissions may be made on a reverse link channel, such as the R-DCCH. Alternatively, the reverse link channels allocated for communication may include: such as a reverse common control channel (R-CCCH), a reverse fundamental channel (R-FCH), or a reverse supplemental channel (R-SCH).

The allocation of the R-SCH may be unlimited. The assignment is withdrawn when the member subscriber station informs the sector via the R-DCCH that communication has ended, such that the sector detects that member subscriber station transmissions have ceased for a predetermined amount of time. The base station may then assign the R-SCH to another member subscriber station to be transmitted to the group. There is at most one member subscriber station transmitting at a given time, so there is at most one R-SCH in all sectors containing active member subscriber stations supporting the group call.

As described above, in one embodiment the member subscriber stations are not assigned a separate R-DCCH, but use the R-EACH for reverse link signaling and communications when needed. Thus, a request to transmit a grant is issued using the R-EACH, or R-EACH and R-CCCH. The R-EACH or R-EACH/R-CCCH IS used in the basic access, memory access and power control access modes defined in the IS-2000 standard.

Upon receiving the request, the base station assigns member subscriber stations R-FCH, R-DCCH, R-CCCH, or R-SCH and sends a grant to start transmission over the forward channel monitored by the member subscriber stations. Thus, if there has been recent group activity and the member user group is monitoring the forward link broadcast channel, a grant is issued on the forward link broadcast channel, such as the F-SCH, F-CCCH/F-BCCH, or F-DCCH that is monitored by the member user station. If the member subscriber station releases the forward link shared channel or F-DCCH, the permission is sent out on the F-PDH and the F-CCCH. In this case, signaling messages must also be sent to all member subscriber stations in its sector to begin monitoring the forward link broadcast channel, and control/signaling the forward channel (if used).

If the member subscriber station requiring transmission IS granted either R-FCH or R-DCCH, the procedure for establishing and releasing either R-FCH or R-DCCH IS performed in accordance with the IS-2000 standard. Signaling between the active member subscriber station and the system occurs on the assigned R-FCH or R-DCCH or R-EACH/CCCH.

If a member subscriber station requiring transmission is granted the R-CCCH, the R-CCCH is exclusively assigned by the sector to the member subscriber station for a predetermined period to avoid collision with other member subscriber stations, or is shared for efficiency.

If the member subscriber station requesting transmission is granted the R-SCH, the R-SCH is assigned exclusively to that member subscriber station by the sector for a predetermined period. The allocation of the R-SCH may be infinite for user data transmission. The assignment terminates when the member subscriber station informs the sector via the R-EACH that its talk portion has ended, or when the sector detects that the member subscriber station is no longer transmitting. The sector may then assign another member subscriber station to transmit on the R-SCH.

On the other hand, transmissions shorter than the threshold to the group occur on the R-EACH without requesting a grant exchange. Basic access, memory access, and power control access are three illustrative embodiments that apply to these channels and are defined in IS-2000. In this embodiment, sending from the member user group to the group longer than the threshold must follow a request-grant exchange.

In the above embodiment, the member subscriber station must send a request and receive permission before beginning transmission on the assigned reverse link channel. The channel assignment and the transmit grant are not necessarily two different requests. Reverse channel assignment occurs at a lower level, e.g., a sector, while transmit grants are at a higher level, e.g., a group call administration. Thus, in one embodiment, the member subscriber station begins transmitting after channel assignment. This means that a transmit permission has been given.

Silence period determination

To reduce waste, only the member subscriber stations are assigned a forward link shared channel during an active group call. Thus, the sector and member subscriber stations must be able to determine the beginning of the silence period. The term silence period is used herein to identify a dormant or idle state. The silent period starts, for example, because there is no longer a request to send a group for a predetermined period of time, or because a scheduled schedule for a group call has expired. In one embodiment, the decision is made by the access network and the member subscriber stations are notified. Alternatively, the attendant subscriber station decides the start of a silent period from a long period of activity and automatically transitions to dormant/idle mode, notifying or not notifying the sector. In another embodiment, the member user stations and the access network transition to silent periods according to separate schedules.

Upon determining the beginning of the silence period, the member subscriber stations transition to slotted mode operation, simply periodically monitoring the group call for common channels or common channels for an optionally provided Quick Paging Channel (QPCH).

Alternatively, the group of member users is transferred to a paging channel (F-PCH, or a combination of F-CCCH and F-BCCH, each optionally associated with a QPCH) which they will regularly monitor.

If the member subscriber station is monitoring the F-SCH and F-DCCH during active periods, then the F-DCCH is monitored during silent periods.

In an alternative embodiment of fig. 3, the control entity monitors the group active for group call related F-CCCH and F-BCCH and monitors another-F-CCCH or a pair of F-CCCH/F-BCCH for regular paging and messaging through the sector allocation member subscriber stations.

In an alternative embodiment of fig. 4, the control entity monitors a group of F-CCCHs and F-BCCHs for group activity, for regular pages, for F-CCCHs, for PQCHs associated with regular paging F-CCCHs, and for point-to-multipoint service signaling, through the sector allocation member subscriber stations. The member subscriber station continuously monitors the groups F-CCCH and F-BCCH, and the allocated locations on the F-BCCH and QPCH (called paging indicators in IS-2000), and decides for the member subscriber station whether it needs to monitor its allocated regular paging F-CCCH as well.

Active period notification

Once the active period begins, the member subscriber stations are notified by a message sent on the forward link channel monitored by the member subscriber stations during silence.

In one embodiment, the forward link channel used by each member subscriber station in the active state is a forward common control channel (F-CCCH), a forward broadcast common channel (F-BCCH), or both a F-CCCH or a F-BCCH.

In one embodiment, all F-CCCH and F-BCCH are shared by member subscriber stations of the group call and non-members of a given sector that are needed for their paging. This is achieved by having the appropriate access information in the transmissions on these forward link channels.

In another embodiment, some of the F-CCCHs and F-BCCHs in a sector are exclusively allocated for subscriber group calls, and the remaining F-CCCHs and F-BCCHs are exclusively allocated for paging of non-member subscriber stations.

Those skilled in the art will recognize that while various embodiments have been described in terms of flowcharts and methods, this is for illustration only. The method may be implemented by an apparatus that in one embodiment includes a processor coupled to a transmitter, a receiver, and any other suitable AT and/or AP blocks.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality in order to clearly illustrate the interchangeability of such hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with the following: a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a field programmable array gate (EPGA), or other programmable logic device, discrete gated transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known to those skilled in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the patent and trademark office patent file or records, but otherwise is in the copyright owner in any event.

Claims (27)

1. A method for channel management in a communication system, comprising:

allocating at least one forward link shared channel during an active period for subscriber stations belonging to a group;

allocating at least one forward link channel during a silence period for said subscriber station; and

during an active period for each of said subscriber stations, a forward link dedicated channel is allocated.

2. The method of claim 1, wherein the assigned at least one forward link channel is modulated with information about point-to-point services and point-to-multipoint services.

3. The method of claim 1, wherein said allocating at least one forward link channel during a silence period for said subscriber station comprises:

allocating at least one forward link channel modulated by information about the point-to-point service; and

allocating at least one forward link channel modulated by the information on the point-to-multipoint service.

4. The method of claim 1, wherein the allocated forward link shared channel is modulated by user data and control data.

5. The method of claim 1, wherein the allocated forward link shared channel is modulated by user data; and is

The allocated forward link dedicated channel is modulated by control data.

6. A method for channel management in a communication system, comprising:

allocating at least one reverse link dedicated channel during an active period for each subscriber station belonging to a group;

modulating, by active subscriber stations belonging to the group, the at least one reverse link dedicated channel with user data and control data; and

the at least one reverse link dedicated channel is modulated with control data by passive subscriber stations belonging to the group.

7. A method of channel management in a communication system, comprising:

allocating at least one reverse link dedicated channel to active subscriber stations belonging to a group;

allocating at least one reverse link common channel to passive subscriber stations belonging to a group; and

modulating the at least one reverse link common channel with control data.

8. The method of claim 7, comprising: modulating the at least one reverse link dedicated channel with user data and control data.

9. The method of claim 7, further comprising:

modulating the at least one reverse link common channel with a request for a reverse link channel assignment; and

the assigned reverse link channel is modulated with control data.

10. An apparatus for channel management in a communication system, comprising:

means for allocating at least one forward link shared channel during an activity period for subscriber stations belonging to a group;

means for allocating at least one forward link channel during a silence period for said subscriber station; and

means for allocating a forward link dedicated channel during an active period for each of said subscriber stations.

11. The apparatus of claim 10, wherein the assigned at least one forward link channel is modulated with information about point-to-point services and point-to-multipoint services.

12. The apparatus of claim 10 wherein said means for allocating at least one forward link channel during a silence period for a subscriber station comprises:

means for allocating at least one forward link channel modulated with information about a point-to-point service; and

means for allocating at least one forward link channel modulated with information regarding the point-to-multipoint service.

13. The apparatus of claim 11, wherein the allocated forward link shared channel is modulated by user data and control data.

14. The apparatus of claim 10, wherein the allocated forward link shared channel is modulated by user data; and

the allocated forward link dedicated channel is modulated by control data.

15. An apparatus for channel management in a communication system, comprising:

means for allocating at least one reverse link dedicated channel during an active period for each subscriber station belonging to a group;

means for modulating said at least one reverse link dedicated channel with user data and control data by active subscriber stations belonging to said group; and

means for modulating the at least one reverse link dedicated channel with control data by passive subscriber stations belonging to said group.

16. An apparatus for channel management in a communication system, comprising:

means for allocating at least one reverse link dedicated channel to active subscriber stations belonging to a group;

means for assigning at least one reverse link common channel to passive subscriber stations belonging to a group; and

means for modulating the at least one reverse link common channel with control data.

17. The apparatus of claim 16, further comprising:

means for modulating the at least one reverse link dedicated channel with user data and control data.

18. The apparatus of claim 16, further comprising:

means for modulating the at least one reverse link common channel with a request for a reverse link assignment; and

means for modulating the assigned reverse link channel with control data.

19. An apparatus for channel management in a communication system, comprising:

a control unit at an access network configured to:

allocating at least one forward link shared channel during an active period for subscriber stations belonging to a group; and

allocating at least one forward link channel during silence for the subscriber station;

allocating a forward link dedicated channel during an active period of each of said subscriber stations; and

a sector communicatively coupled to the control unit, the sector configured to transmit information regarding an allocation of the control unit.

20. The apparatus of claim 19, wherein the assigned at least one forward link channel is modulated with information about point-to-point services and point-to-multipoint services.

21. The apparatus as claimed in claim 19, wherein said control unit assigns at least one forward link channel during the silence period for the subscriber station by being configured to:

allocating at least one forward link channel modulated with the relevant point-to-point service information; and

at least one forward link channel modulated with the information regarding the point-to-multipoint service is allocated.

22. The apparatus of claim 19, wherein the allocated forward link shared channel is modulated with user data and control data.

23. The apparatus of claim 19, wherein the allocated forward link shared channel is modulated with user data; and is

The allocated forward link dedicated channel is modulated with control data.

24. An apparatus for channel management in a communication system, comprising:

a control unit at the access network configured to allocate at least one reverse link dedicated channel during an active period for each subscriber station belonging to a group;

active subscriber stations belonging to the group configured to modulate the assigned at least one reverse link dedicated channel with user data and control data; and

a passive subscriber station belonging to the group configured to modulate the assigned at least one reverse link dedicated channel with control data.

25. An apparatus for channel management in a communication system, comprising:

a control unit at an access network configured to:

allocating at least one reverse link dedicated channel to active subscriber stations belonging to a group; and

allocating at least one reverse link common channel to passive subscriber stations belonging to said group;

a sector communicatively coupled to the control unit, the sector configured to transmit information regarding an allocation of the control unit; and

a passive subscriber station belonging to the group configured to modulate the assigned at least one reverse link common channel with control data.

26. The apparatus of claim 25, further comprising:

active subscriber stations belonging to said group configured to modulate said at least one reverse link dedicated channel with user data and control data.

27. The apparatus of claim 25, wherein a passive subscriber station belonging to the group is further configured to:

modulating the at least one reverse link common channel with a request for a reverse link channel assignment; and

modulating the assigned reverse link channel with control data.