Efficient multicasting for packet data systems

ES 2 328 166 T3 description

Efficient multicast for packet data systems.

Field

The present invention relates generally to communications and more specifically to multi-broadcast transmission in wireless communication systems.

Background

The field of wireless communications has many applications, including eg. eg, cordless telephones, messaging, wireless local loops, electronic agendas, Internet telephony, and satellite communication systems. A particularly important application is cellular telephone systems for mobile subscribers. As used herein, the term "cellular" system encompasses both personal and cellular communications service (PCS) frequencies. Various over-the-air interfaces have been developed for such cellular telephone systems, including, e.g. eg, frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA). In relation to this, various domestic and international standards have been established, including, p. eg, the Advanced Mobile Telephone Service (AMPS), the Global System for Mobile Phones (GSM) and the Provisional Standard 95 (IS-95). The IS-95 and its derivatives, IS-95A, IS95B, ANSI J-STD-008 (often referred to here collectively as IS-95), and the proposed high data rate systems, are promulgated by the Industry Association of Telecommunication (TIA) and other well-known standardization bodies.

Cellular phone systems configured using the IS-95 standard employ CDMA signal processing techniques to provide highly efficient and robust cellular phone service. Examples of cellular telephone systems configured essentially in accordance with the use of the IS-95 standard are described in US Patent Nos. 5,103,459 and 4,901,307, which are assigned to the assignee of the present invention, and incorporated herein by reference. An example of a system using CDMA techniques is the Radio Transmission Technology (TTR) Candidate Proposal cdma2000 ITU-R (referred to herein as cdma2000), published by the TIA. The standard for cdma2000 is provided in draft versions of IS-2000, and has been approved by the TIA and 3GPP2. Another CDMA standard is the W-CDMA standard, as performed in the 3 Partnership Project^to Generation "3GPP", Documents No. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213 and 3G TS 25.214.

The aforementioned telecommunication standards are examples of some of the various communication systems that can be implemented to transmit voice and / or data. Within these systems, multiple users must share limited system resources. One such limitation is the availability of channels to support multiple users. For example, in a CDMA type system, each user within the scope of a base station is allocated one or more channels to communicate with the base station. If there were not enough channels, then a new user who is entering the scope of the base station would be prevented from accessing the services of that base station.

In certain situations, it is desirable to transmit the same data to multiple users. This is especially desirable for applications that incur a heavy load on the wireless network, such as streaming videos. However, cellular base stations are currently configured to transmit data on separate channels to each user, regardless of the similarity of the data for each user. Hence, it could be said that the base station is wasting channel resources every time the base station makes multiple transmissions with the same data content. There is a current need in the art for a method and apparatus for transmitting identical or similar data to multiple users without using multiple channels. Additional attention is called to EP-A-0 999 656, which discloses a multi-broadcast communication system, comprising: a base station transmitting a multi-broadcast message over a single communication channel; and multiple mobile terminals that receive the multicast message on the single communication channel; wherein each of the mobile terminals comprises: a receiver for receiving the multicast message; a counter for measuring a reception power of the multicast message, and for judging whether or not the reception power is sufficient; a first transmitter for transmitting a transmission power increase request signal, for requesting the base station to increase a transmission power of the multicast message; and a switch for enabling transmission of the transmission power increase request signal to the base station, when it is determined that the reception power of the multicast message is not sufficient; wherein the base station comprises: a second transmitter for transmitting the multicast message; a transmit power controller, for controlling the transmit power of the broadcast message transmitted from the second transmitter; and a receiver for receiving the transmission power increase request signal, which has been transmitted by the mobile terminal; and wherein the transmit power controller increases the transmit power of the multicast message when the base station receives the transmit power increase request signal.

According to the present invention, there are provided an apparatus for multi-broadcast transmissions, as set forth in claim 1, and a method for multi-broadcast transmissions, as set forth in claim 5. Embodiments of the invention are claimed in the dependent claims.

ES 2 328 166 T3

Summary

The procedures and apparatus presented here address the above needs.

Brief description of the drawings

Fig. 1 is a diagram of a wireless communication network.

Fig. 2 is a flow chart of an embodiment for selecting the timing of a multicast transmission.

Fig. 3 is a flow chart of an embodiment for selecting the transmission format of a multicast transmission.

Detailed description

As illustrated in Fig. 1, a wireless communication network 10 generally includes a plurality of mobile stations (also called subscriber units or user equipment or remote stations) 12a-12d, a plurality of base stations (also called base station transceivers (TEB) or Node B) 14a-14c, a base station controller (CEB) (also called a radio network controller or packet control function 16), a mobile switching center (CCM) or switch 18, a packet data server node (NSDP) or intranet function (FIR) 20, a public switched telephone network (PSTN) 22 (typically, a telephone company), and an Internet Protocol (IP) network 24 (typically, Internet). For the sake of simplicity, four mobile stations 12a-12d, three base stations 14a-14c, one CEB 16, one CCM 18, and one NSDP 20 are shown. Those skilled in the art will understand that there could be any number of mobile stations 12, base stations 14, CEB 16, CCM 18, and NSDP 20.

In one embodiment, the wireless communication network 10 is a packet data service network. Mobile stations 12a-12d can be any of a number of different types of wireless communication devices, such as a portable phone, a cell phone that is connected to a laptop running IP-based, web browser applications, a cell phone with associated hands-free car kits, an electronic diary running IP-based, web browser applications, a wireless communication module incorporated in a laptop computer, or a fixed-location communication module, such as might be found in a wireless local loop or meter reading system. In the most general embodiment, the mobile stations can be of any type of communication unit. Mobile stations 12a12d can be advantageously configured to implement one or more wireless packet data protocols, such as those described, for example, in the EIA / TIA / IS-707 standard.

In one embodiment, IP network 24 is coupled with NSDP 20, NSDP 20 is coupled with CCM 18, CCM 18 is coupled with CEB 16 and PSTN 22, and CEB 16 is coupled with base stations 14a. -14c via lines configured for the transmission of voice and / or data packets, according to any of several known protocols, including, eg. eg, E1, T1, Asynchronous Transfer Mode (ATM), IP; PPP, Frame Relay, HDSL, ADSL or xDSL. In an alternative embodiment, CEB 16 is directly coupled to NSDP 20, and CCM 18 is not coupled to NSDP 20.

During typical operation of wireless communication network 10, base stations 14a-14c receive and demodulate reverse signal sets from various mobile stations 12a-12d participating in telephone calls, Web browsing, or other data communications. Each reverse signal received by a given base station 14a-14c is processed within that base station 14a-14c. Each base station 14a-14c can communicate with a plurality of mobile stations 12a-12d, modulating and transmitting sets of direct signals to mobile stations 12a12d. For example, as shown in FIG. 1, base station 14a simultaneously communicates with first and second mobile stations 12a, 12b, and base station 14c simultaneously communicates with third and fourth mobile stations 12c, 12d.

CEB 16 provides mobility management and call resource allocation functionality, including orchestrating soft handoffs of a call for a specific mobile station 12a-12d from one base station 14a-14c to another base station 14a-14c. For example, a mobile station 12c is simultaneously communicating with two base stations 14b, 14c. Eventually, when the mobile station 12c gets far enough away from one of the base stations 14c, the call will be handed over to the other base station 14b.

If the transmission is a conventional telephone call, the CEB 16 will route the received data to the CCM 18, which provides additional routing services for the interface with the PSTN 22. If the transmission is a packet-based transmission, such as a data call Intended for the IP network 24, the CCM 18 will route the data packets to the NSDP 20, which will forward the packets to the IP network 24. Alternatively, the CEB 16 will route the packets directly to the NSDP 20, which forwards the packets to the IP network 24.

In some communication systems, packets carrying data traffic are divided into sub-packets, which occupy slots in a transmission channel. For illustrative ease only, the nomenclature of a system is used here

ES 2 328 166 T3 cdma2000. Such use is not intended to limit the implementation of the embodiments present herein to cdma2000 systems. The embodiments can be implemented in other systems, such as, e.g. eg, WCDMA, without affecting the scope of the embodiments described herein.

The direct link from the base station to a remote station operating within the range of the base station may comprise a plurality of channels. Some of the forward link channels may include, but are not limited to, a pilot channel, a sync channel, a messaging channel, a fast messaging channel, a broadcast channel, a power control channel, a channel, a control channel, a dedicated control channel, a media access control (MAC) channel, a fundamental channel, a supplemental channel, a supplemental code channel, and a packet data channel. The reverse link from a remote station to a base station also comprises a plurality of channels. Each channel carries different types of information to the final destination. Typically, voice traffic is carried over fundamental channels, and data traffic is carried over supplementary channels or packet data channels. Supplementary channels are usually dedicated channels, while packet data channels usually carry signals that are allocated to different participants in a time and code multiplexed manner. Alternatively, packet data channels are also described as shared overhead channels. For the purpose of describing the embodiments herein, the overhead channels and the packet data channels are generically referred to as data traffic channels.

Voice traffic and data traffic are typically scrambled, modulated, and spread prior to transmission over the forward or reverse links. Coding, modulation, and spreading can be implemented in various formats. In a CDMA system, the transmission format ultimately depends on the type of channel on which voice traffic and data traffic are being transmitted, and on the condition of the channel, which can be described in terms of fading and interference.

Packet data systems traditionally transmit data to remote stations, between one and ten stations at a time. Data transmission takes place from a base station over a shared data traffic channel, which is accompanied by control information. The control information may comprise data transmission parameters, such as modulation, encoding, and power, which are adjusted by the base station using Channel Quality Response (RCC) information about the remote station. The RCC information is used to maximize system throughput, minimize channel utilization, and maximize the probability that a data transmission will reach the remote station with reasonable quality. The RCC can be explicit through a transmission from the remote station, or the RCC can be derived by the base station through transmit power levels. The base station transmits the control information in order to assist the remote station in decoding the associated data stream.

One element of control information that is transmitted to the remote station is a media access control identifier (MAC_ID). MAC_IDs are assigned to remote stations according to an International Mobile Station Identification (IIEM) when remote stations enter the communication system. Therefore, the channel that is dedicated to the remote station can be identified by the MAC_ID that is assigned to the remote station.

Some packet data systems offer services such as multicast and broadcast. In a multicast, the same transmissions are sent to a group of remote stations. In a broadcast, the same transmissions are sent to all remote stations in range of the base station. For example, a video broadcast would require the system to broadcast the video stream to all users subscribed to the video stream channel. However, as mentioned above, packet data systems are configured to transmit data to only one remote station at a time. Therefore, multicast and broadcast in today's packet data systems require independent transmission of the same data to each remote station. If N remote stations were present in the system, and the system needed to broadcast the same message to all remote stations, then the system would transmit the same information N times, with each transmission customized to the needs of each remote station.

The same information is sent independently to each remote station, because a transmission to each remote station would propagate through different channel conditions. The condition of each channel will vary based on distance to the base station, fading, and interference from other channels. In order to ensure the delivery of the information within a desired quality level, such as a frame error rate (TET) of less than 1%, the various transmission parameters can be adjusted. As a simplistic example, if the channel conditions were bad, then the base station would transmit information to a remote station using a format where the data symbols are often repeated in the packet. Thus, the receiving party could software combine any corrupted data symbols to obtain the original information. However, if the channel conditions are good, then the base station could transmit information to a remote station using a format that does not repeat data symbols, since the receiving party is likely to receive the uncorrupted data symbols. Therefore, although the same information is being transported to the remote stations, the transmission formats of the data packets for each remote station may be different.

An example of the different transmission parameters, at different speeds, that can be used by a communication network, is shown in Table 1.

ES 2 328 166 T3

TABLE 1

Direct Link Modulation Parameters

<td>Speed ​​of Data (kbps)</td><td>Number of Slots</td><td>Bits per Package</td><td>Code Rate</td><td>Modulation</td>

<td> 38,4</td><td> 16</td><td> 1024</td><td> 1 /5</td><td>QPSK</td>

<td> 76,8</td><td> 6</td><td> 1024</td><td> 1 /5</td><td>QPSK</td>

<td> 153,6</td><td> 4</td><td> 1024</td><td> 1 /5</td><td>QPSK</td>

<td> 307,2</td><td> 2</td><td> 1024</td><td> 1 /5</td><td>QPSK</td>

<td> 614,4</td><td> 1</td><td> 1024</td><td> 1 /3</td><td>QPSK</td>

<td> 307,2</td><td> 4</td><td> 2048</td><td> 1 /3</td><td>QPSK</td>

<td> 614,4</td><td> 2</td><td> 2048</td><td> 1 /3</td><td>QPSK</td>

<td> 1228,8</td><td> 1</td><td> 2048</td><td> 2/3</td><td>QPSK</td>

<td> 921,6</td><td> 2</td><td> 3072</td><td> 1 /3</td><td>8-PSK</td>

<td> 1843,2</td><td> 1</td><td> 3072</td><td> 2/3</td><td>8-PSK</td>

<td> 1228,8</td><td> 2</td><td> 4096</td><td> 1 /3</td><td>16-QAM</td>

<td> 2457,6</td><td> 1</td><td> 4096</td><td> 2/3</td><td>16-QAM</td>

It should be noted that Table 1 is merely an illustrative example of only some of the transmission parameters that may be different for a transmission to one subscriber versus a transmission to other subscribers. Other parameters, such as symbol repetition and transmission duration in multiple frames, are not shown.

The present embodiments are directed toward eliminating the waste of channel resources that results from the multiplicity of identical broadcasts to multiple recipients. In one embodiment, the base station generates a special MAC_ID value that identifies a group of remote stations, rather than a single remote station. For each available multicast service, a corresponding special MAC_ID value is also generated. For example, the MAC_ID 00203 could be reserved for the video stream of a television channel. Remote stations wishing to receive the television channel through the communication system would subscribe to this service, and would wait for the MAC_ID 00203 in the control signaling information.

Since the MAC_ID only identifies a channel that will be demodulated and decoded by all subscriber remote stations, embodiments to allow each remote station in the subscriber group to demodulate and decode the channel are also described here. Fig. 2 is a flow chart for selecting the timing of a multicast to M subscribers. In step 200, a scheduling item at a base station determines the channel quality response indicators of M subscribers for a multicast service. The programming element may comprise a memory element and a processing element that is configured to execute the procedural steps described herein. In one embodiment, the interference per channel (I / C) measurements of the forward link common pilot signal serve as channel quality response indicators. In step 210, the scheduling element selects an optimal time to transmit the multicast on a channel marked with a special MAC_ID. The optimal time is selected by determining when the subscriber in the worst location has good channel conditions, or the delay in data transmission becomes too long. For example, channel conditions could be unfavorable for a subscriber who is traveling at extremely high speeds near the base station. High speed could cause random, but short-lived, intense fading. Such short duration severe fades would be an unfavorable channel condition, which would decrease the data throughput of the system. In step 220, the base station encodes the multicast data in such a way as to allow reception at an acceptable level of quality by the subscriber with the worst channel conditions. The base station then encrypts the multicast scrambled data, as required, with an encryption code that is known to all subscribers, and transmits it at the selected time on the channel specified by the MAC_ID. In step 230, the base station transmits using the modulation scheme and power level that allow the subscriber with the worst channel conditions to receive the multicast with an acceptable quality level. A further refinement of the embodiment is the use of a scrambling code that is common to all subscribers, or common to a selected group of subscribers who have paid for extra services.

ES 2 328 166 T3

In an alternative embodiment, instead of using the I / C as the channel quality response indicator, the scheduling element determines when the worst-location subscriber has good channel conditions by transmitting test data packets to the subscriber of worst location, until acknowledgment signals arrive from the worst location subscriber. Once acknowledgment signals arrive, indicating the successful demodulation and decoding of the test data packet, the scheduling element can begin multicasting.

In another alternative embodiment, the scheduling element transmits test data packets to all subscribers and waits for acknowledgment signals from a predetermined percentage of subscribers. The percentage could take all the values ​​between a simple majority of the subscribers and 100% of the subscribers. The effective value of the percentage can be chosen by the server system. In a system where the acknowledgment signals are scheduled to arrive at predetermined times, this embodiment can be set such that multicasting takes place when at least one indicated subscriber has transmitted an acknowledgment signal. The indicated subscriber (s) may be chosen in order to maximize the likely reception of the multicast by the majority of subscribers.

It should be noted that it is unlikely that a subscriber in a good locality will not successfully receive the test data packets or multicast. If a base station does not receive an acknowledgment signal from this subscriber, the base station is more likely to have lost the reverse link acknowledgment signal, rather than a failed reception of the forward link signal by the subscriber. . Therefore, it is more important to focus on the acknowledgment signals from subscribers with weak channels, rather than subscribers with favorable channels.

Fig. 3 is a flow chart for selecting the transmission format of a multicast to M subscribers. In step 300, a scheduling item at a base station determines the M subscriber channel quality response indicators for a multicast service. Based on the channel quality response indicators, the scheduling element determines the temporal sensitivity of the data and the data transmission formats. In step 310, the scheduling element selects a transmission format that will allow the subscriber with the worst channel conditions to recover the original data. In step 320, the base station transmits the multicast in the transmission format selected by the scheduling item, where the multicast is transmitted using a single CAM_ID. It should be noted that the other subscribers would not have difficulties in decoding the multicast using the selected transmission format, since all the other subscribers have better channel conditions. As an alternative to using the single ID_CAM, the multicast is encrypted with an encryption code known only to subscribers.

In addition to the steps described above, the scheduling element could also send retransmissions in the format indicated by the subscriber with the worst channel conditions. Retransmissions are redundant transmissions of information, which have already been transmitted. Through the "software merge" process at the receiver, symbols that have become corrupted during the transmission of one packet can be combined with symbols that have become corrupted during the transmission of another packet. Thus, the "good" symbol bits from the various transmissions can be used together to recover the original information from the data.

As mentioned above, it is possible to have multiple special CAMIDs for each possible broadcast service. It is envisioned that the above-described embodiments may allow a service provider to offer multiple multi-broadcast services, such as news, weather, sports, stock quotes, etc., without sacrificing channel resources that could otherwise be used for the broadcast. voice traffic and dedicated data traffic.

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

Those skilled in the art will further appreciate that the various illustrative logic 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. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above, generally, in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Skilled artisans can implement the described functionality in a variety of ways for each specific application, but such implementation decisions should not be construed as deviating from the scope of the present invention.

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or realized with a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an array. field programmable gate (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described here. A

ES 2 328 166 T3 general purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller or state machine. A processor can also be implemented as a combination of computing devices, e.g. eg, 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 similar configuration.

The steps of a procedure or algorithm described in relation to the embodiments described herein can be performed directly in hardware, in a software module executed by a processor, or in a combination of both. A software module can 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 in the art. An example of a storage medium is coupled with the processor, such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium can be integrated into the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can reside as discrete components in a user terminal.

The foregoing description of the disclosed embodiments is provided to enable anyone skilled in the art to make or use the present invention. Various modifications to these embodiments will be immediately apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention, as defined in the dependent claims.

Application theming

1. An apparatus for multi-broadcast transmissions that minimize channel resources, comprising:

a memory element; and a processing element for executing a set of instructions stored in the memory element, the set of instructions being for:

generating an identifier for a group of subscribers, wherein the identifier is for accessing a multicast service;

using channel quality information for at least one subscriber, in order to determine the timing of the multicast service to the group of subscribers; and transmitting the identifier and the multicast service on at least one channel, wherein the multicast service is transmitted according to the timing determined by the channel quality information.

2. The apparatus of 1, in which the transmission of the identifier and the multicast service on at least one channel comprises:

transmit the identifier on a first channel; and transmitting the multicast on a second channel.

3. The apparatus of 2, in which the processing element is additionally to execute instructions in order to:

encrypting the multicast service before transmitting the multicast service on the second channel, in which the encryption is performed using a code known only to the group of subscribers.

Four. The apparatus of 1, in which the use of the channel quality information for at least one subscriber, in order to determine the timing of the multicast service, comprises:

choosing the channel quality information by selecting the channel quality information associated with the subscribers with the worst channel conditions; and determining the timing of the multicast service according to the subscribers with the worst channel conditions.

5. The apparatus of 4, in which the channel quality information is a measurement of the channel interference of the forward link common pilot signal.

6. The apparatus of 4, in which the channel quality information is derived from the transmit power levels of a base station.

7. The apparatus of 4, in which the channel quality information is a plurality of acknowledgment signals:

ES 2 328 166 T3

8. The apparatus of 7, in which the choice of the channel quality information of the subscribers with the worst channel conditions comprises:

transmit a plurality of test data packets to the group of subscribers:

waiting for a plurality of subscriber group acknowledgment signals, in response to the plurality of test data packets; and transmitting the multicast service if the plurality of acknowledgment signals indicate a response from a predetermined percentage of the subscriber group.

9. The apparatus of 1, in which the use of the channel quality information for at least one subscriber, in order to determine the timing of the multicast service, comprises:

choosing the channel quality information of the subscriber with the worst channel conditions;

determining the timing of the multicast service according to the subscriber with the worst channel condition.

10. The apparatus of 9, in which the channel quality information is an acknowledgment signal from the subscriber with the worst channel condition.

eleven. An apparatus for multi-broadcast transmissions that minimize channel resources, comprising a memory element; and a processing element for executing a set of instructions stored in the memory element, the set of instructions being for:

generating an identifier for a group of subscribers, in which the identifier is used to access a multicast service;

using the channel quality information for at least one subscriber, in order to determine the transmission format of the multicast service to the group of subscribers; and transmitting the identifier and the multicast service on at least one channel, in which the multicast service is transmitted according to the transmission format determined by the channel quality information.

12. The apparatus of 11, in which the transmission of the identifier and the multicast service on at least one channel comprises:

transmit the identifier on a first channel; and transmitting the multicast on a second channel.

13. The apparatus of 12, in which the processing element is additionally to execute instructions in order to:

encrypting the multicast service before transmitting the multicast service on the second channel; wherein the encryption is carried out using a code known only to the group of subscribers.

14. The apparatus of 11, in which the use of the channel quality information, for at least one subscriber, in order to determine the transmission format of the multicast service, comprises:

choosing the channel quality information by selecting the channel quality information associated with the subscribers with the worst channel conditions; and determining the transmission format of the multicast service according to the subscribers with the worst channel conditions.

fifteen. The apparatus of 14, in which the channel quality information is a measurement of channel interference from the forward link common pilot signal.

16. The apparatus of 14, in which the channel quality information is derived from the transmission power levels of a base station.

17. The apparatus of 14, in which the channel quality information is a plurality of acknowledgment signals.

ES 2 328 166 T3

18. The apparatus of 17, in which the selection of the channel quality information of the subscribers with the worst channel conditions comprises:

transmitting a plurality of test data packets to the group of subscribers;

waiting for a plurality of acknowledgment signals from the group of subscribers, in response to the plurality of test data packets; and transmitting the multicast service if the plurality of acknowledgment signals indicate a response from a predetermined percentage of the subscriber group.

19. The apparatus of 11, in which the use of the channel quality information, for at least one subscriber, in order to determine the transmission format of the multicast service, comprises:

choosing the channel quality information of the subscriber with the worst channel conditions;

determining the transmission format of the multicast service according to the subscriber with the worst channel condition.

twenty. The apparatus of 19, in which the channel quality information is an acknowledgment signal from the subscriber with the worst channel condition.

twenty-one. An apparatus for multi-broadcast transmissions that minimize channel resources, comprising:

a memory element; and a processing element for executing a set of instructions stored in the memory element, the set of instructions being for:

determining channel quality information for a plurality of subscribers;

identify the subscriber with the worst channel conditions;

encrypting a multicast service using an encryption code known to the plurality of subscribers; and transmitting the encrypted multicast service to the plurality of subscribers, wherein the encrypted multicast service is transmitted in accordance with a transmission format that is optimal for the subscriber with the worst channel conditions.

22. A method for broadcasting to a group of subscribers in a cellular communication network, comprising:

determining channel quality information for a plurality of subscribers;

identify the subscriber with the worst channel conditions;

encrypting a multicast service using an encryption code known to the plurality of subscribers; and transmitting the encrypted multicast service to the plurality of subscribers, wherein the encrypted multicast service is transmitted in accordance with a transmission format that is optimal for the subscriber with the worst channel conditions.

2. 3. A method for broadcasting to a group of subscribers in a cellular communication network, comprising:

generating an identifier for a group of subscribers, wherein the identifier is for accessing a multicast service;

using channel quality information for at least one subscriber, in order to determine the timing of the multicast service to the group of subscribers; and transmitting the identifier and the multicast service on at least one channel, wherein the multicast service is transmitted according to the timing determined by the channel quality information.

24. A method for broadcasting to a group of subscribers in a cellular communication network, comprising:

generating an identifier for a group of subscribers, wherein the identifier is for accessing a multicast service;

ES 2 328 166 T3 use channel quality information for at least one subscriber, in order to determine the transmission format of the multicast service to the group of subscribers; and transmitting the identifier and the multicast service on at least one channel, wherein the multicast service is transmitted according to the transmission format determined by the channel quality information.

25. A procedure for efficient multi-release, comprising:

generating an identifier for a group of subscribers, wherein the identifier is for accessing a multicast service;

identifying the subscriber with the worst channel quality by analyzing a plurality of channel quality response indicators among a group of subscribers;

selecting a timing and transmission format of the multicast service, such that the multicast service is received by the subscriber with the worst channel conditions; and transmitting the identifier on a first channel and the multicast service on a second channel, according to the timing and transmission format determined by the subscriber with the worst channel quality.