MXPA06009048A - Transmission of signaling information for broadcast and multicast services - Google Patents

Abstract

Techniques for transmitting signaling information for broadcast and multicast services are described. A base station transmits signaling information for each service in accordance with a schedule that includes a repetition period and a modification period. The signaling information is sent in each repetition period to allow wireless devices to quickly obtain this information. Changes to the critical signaling information are permitted at the start of each modification period, which is an integer multiple of the repetition period. Whenever the critical signaling information for a given service is changed in a given modification period, a notification indicator for the service is set in an entire preceding modification period to inform the wireless devices of the impending change. The wireless devices can detect the notification indicator being set in the preceding modification period and can retrieve the updated critical signaling information in the following modification period.

Description

TRANSMISSION OF SIGNALING INFORMATION FOR BROADCAST AND MULTI-DIFFUSION SERVICES FIELD OF THE INVENTION The present invention generally relates to communication, and very specifically to techniques for transmitting signaling information for broadcast and multicast services in a communication system.

BACKGROUND OF THE INVENTION A communication system can provide unicast, multicast and / or broadcast services. A unicast service provides point-to-point communication between at least one base station and a specific wireless device. A multicast service provides point-to-multipoint communication at least between a base station and a group of wireless devices. A broadcast service provides point-to-multiple point communication between at least one base station and all wireless devices within a designated broadcast area. Some examples of multicast and broadcast services include data and news services, subscription-based services, push-to-talk, and so on. Multicast and broadcast services can send data to wireless devices sporadically, periodically or continuously. The system may need to send signaling information for the broadcast and multicast services supported by the system. The signaling information may also be referred to as overload information, system information, and so on, and may include control information, configuration information, and other pertinent information used to receive services. The system can transmit the signaling information in a control channel. A wireless device that receives one or more services would then monitor the control channel for signaling information sent for the services being received. It is desirable that the wireless device can receive pertinent signaling information from the control channel in a fast and efficient manner to conserve battery power and achieve other benefits. Therefore, there is a need for techniques to transmit signaling information for broadcast and multicast services in a manner to facilitate efficient reception of this information.

SUMMARY OF THE INVENTION Here techniques for transmitting signaling information for broadcast and multicast services are described. In one embodiment, the signaling information is accommodated in two categories called "critical" signaling information and "non-critical" signaling information. The critical signaling information includes signaling information necessary to receive content for services. Non-critical signaling information includes all other signaling information. In one aspect, a base station transmits the signaling information for each service according to a program including, for example, a repetition period, a modification period, and a period of access information. The modification period may be an integer multiple of the repetition period, and the access information period may be an integer divisor of the repetition period. The base station transmits the signaling information in each repetition period of a current modification period to allow the wireless devices to obtain this information quickly. Any change to the critical signaling information in the current modification period is transmitted at the beginning of the next modification period. If the changes to the critical signaling information, for a given service, are transmitted in the next modification period, then a notification indicator for the service is configured so that the entire current modification period informs the wireless devices regarding the imminent changes. The wireless devices can detect the notification indicator that is being configured in the current modification period and can then retrieve the updated critical signaling information in the next modification period. In another aspect, the base station can perform a counting procedure for a given service, to count the number of wireless devices that are receiving the service and to determine the best transmission mechanism to be used for the service. The base station can configure a counting flag for each service at the start of a modification period to enable counting for the service. The base station can send the counting flag for each service as well as access information in each access information period. If a wireless device detects the counting flag set for any service that is being received by the device, then the wireless device reads the access information and attempts to access the system according to the access information. The access information can be changed and the counting flag can be reset in each access information period. Various aspects and embodiments of the invention are described in greater detail below.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a wireless communication system. Figure 2A shows the format of a PICH in a Universal Mobile Telecommunication System (UMTS). Figure 2B shows the format of a frame of the PICH Figures 3A and 3B show transmissions in an MCCH based on a program. Figure 4 shows exemplary transmissions in a MICH and MCCH. Figure 5 shows exemplary transmissions in a PICH, MICH, MCCH and MTCH. Figure 6 shows exemplary transmissions in the MICH and MCCH for counting. Figure 7 shows a process for transmitting the MICH, MCCH, and MTCH through a base station. Figure 8 shows a process for receiving the MICH, MCCH, and MTCH through a wireless device. Figure 9 shows a process for counting by the wireless device. Figure 10 shows a block diagram of the base station and the wireless device.

DETAILED DESCRIPTION OF THE INVENTION The word "exemplary" is used in the present invention to mean "that it serves as an example, case, or illustration." Any modality herein described as exemplary "will not necessarily be construed as being preferred or advantageous over other embodiments." Figure 1 shows a wireless communication system 100 that has the ability to support broadcast and multicast services System 100 includes base stations 110 that engage communication with wireless devices 120. For simplicity, only two base stations 110 and six wireless devices 120 are shown in figure 1. A base station is a fixed station and may also be referred to as a Node B, a base transceiver subsystem (BTS) , an access point, or some other terminology A wireless device can be fixed or mobile and can also be referred to as a user equipment (UE), a mobile station, a terminal, or some other terminology. The radio (RNC) 130 is coupled to the base stations 110 and provides coordination and control for these base stations. It can also be called a base station controller (BSC) or some other terminology. A core network (CN) 132 is coupled to the RNC 130 and other systems and networks, such as a public switched telephone network (PSTN), a packet switched data network, and so on. The core network 132 interconnects the system 100 with these other systems and networks. System 100 may be a Code Division Multiple Access (CDMA) system, a Time Division Multiple Access (TDMA) system, a Frequency Division Multiple Access (FDMA) system, a Division Multiple Access system of Orthogonal Frequency (OFDMA), or some other multiple access system. A CDMA system can execute one or more CDMA (RAT) radio access technologies such as broadband CDMA (W-CDMA) and cdma200. cdma200 covers the IS-2000, IS-856 and IS-95 standards. A TDMA system can execute one or more TDMA RATs and such as Global System for Mobile Communications (GSM). These various RATs and standards are well known in the art. UMTS is a system that uses W-CDMA and / or GSM as radio access technologies and is described in documents of a consortium called "Third Generation Partnership Project" (3GPP). cdma2000 is described in documents of a consortium called "Project 2 of the 3rd Generation Society" (3GPP2). 3GPP and 3GPP2 documents are publicly available. For clarity, the signaling transmission techniques are specifically described below for UMTS. These techniques can be used for multimedia multi-broadcast service (MBMS) in UMTS. In UMTS, a Search Indicator Channel (PICH) is used. to send search indicators to inert wireless devices. An inert wireless device is a wireless device for which the PICH and the MICH are useful. An inactive wireless device can be a wireless device that operates in an inert mode, a wireless device operating in an RRC connected mode but in a CELL_PCH / URA_PCH state. The search indicators for each inert wireless device indicate whether the messages could be sent in a Search Channel (PCH) for the wireless device. The PCH is a transport channel that is carried in a Physical Channel of Secondary Common Control (S-CCPCH). Each inert wireless device monitors the PICH in search of its search indicators.

If these search indicators are set to "1", then the wireless device processes the S-CCPCH to search for any messages sent to the wireless device. Figure 2A shows the PICH format in UMTS.

The PICH is divided into frames, where each frame has a duration of 10 milliseconds (ms). Each frame is identified by a 12-bit system frame number (SFN) that is transmitted simultaneously on a primary CCPCH (P-CCPCH). The SFN is reset to 0 at a specific time, is incremented by one for each subsequent frame, and unwinds around zero after reaching the maximum value of 4095. Each inert wireless device is assigned search occasions, which are specific frames where the wireless device can receive its search indicators. The search occasions for each wireless device are separated by a time interval called a DRX cycle (discontinuous reception mode). The DRX cycle is configurable for each wireless device and is usually 1.28 seconds. In general, the DRX cycle can range from 80 milliseconds (ms) to 5.12 seconds, or from 8 frames to 512 frames. The search occasions for each wireless device are determined based on various parameters including an International Mobile Subscriber Identifier (IMSI), which is an identifier that is unique to each wireless device. Different wireless devices with different IMSIs can be assigned to different search occasions even if they have the same DRX cycle. Figure 2B shows the format of a frame for the PICH. Each PICH frame includes 300 bits, which are labeled as bits bo a b2gg. The first 288 bits are used for Np search indicators, and the last 12 bits are reserved. The number of search indicators (Np) in each PICH frame is configurable by the system and can assume a value of 18, 36, 72 or 144. Each search indicator is sent in 288 / Np consecutive bits in the PICH frame, where 288 / Np can assume a value of 16, 8, 4 or 2. The 288 / Np bits are set to "1" if the search indicator equals "1" and are set to "0" if the search indicator equals "0" The Np search indicators are sent in Np search indicator locations that are numbered from 0 to Np-1 (which are not shown in Figure 2B). Each inert wireless device is mapped to a specific Pl value based on its IMSI. The wireless device is also assigned a search indicator on each search occasion. This search indicator is sent in a location that is determined based on a hash function fp ± (? L, SFN). The location of the search indicator for the wireless device is then determined by both the IMSI for the wireless device and the SFN for the search occasion. In UMTS, an MBMS Indicator Channel (MICH) is used to send MBMS notification indicators (or simply, notification indicators) that indicate whether updated signaling information is being sent in a Point-to-Multiple Point MBMS Control Channel (MCCH) The MCCH is a transport channel that is also ported in the S-CCPCH. The signaling information in the MCCH allows wireless devices to receive a Traffic channel point-to-multiple points MBMS (MTCH). The signaling information can indicate, for example, which services are active, how to decode the MTCH, if the soft combination is possible, and so on. The MTCH is a transport channel that carries traffic or content data for services. The MICH has a format that is similar to the PICH format shown in Figure 2B. Each MICH frame includes 300 bits, which are labeled bits b0 through b299. The first 288 bits are used for Nn notification indicators, and the last 12 bits are reserved. The number of notification indicators (Nn) in each MICH frame is configurable by the system and can assume a value of 18, 36, 72 or 144. Each notification indicator is sent in 288 / Nn consecutive bits in the MICH frame, where 288 / Nn can assume a value of 16, 8, 4 or 2. The Nn notification indicators are sent in Nn indicator locations that are numbered from 0 to Nn-1. Notification indicators can also be sent using the last 12 bits in each PICH frame. Each multicast / broadcast service is mapped to a specific NI value based on a Temporary Mobile Group Identity (TMGI) that identifies that service. Notification indicators are assigned to the service, which are sent in determined locations based on a Hash function fp ± (Pl, SFN). The locations of the notification indicators for the service are then determined by the TMSI for the service and the SFN for the frame. The notification indicators for the service are used to indicate whether the updated signaling information is being sent in the MCCH for the service. Each wireless device monitors the notification indicators for all services desired by the wireless device (or "desired services"). Whenever the notification indicator for any desired service is set to "1", the wireless device further processes the S-CCPCH to look up updated signaling information sent for that service. The MCCH carries signaling information used to support broadcast and multicast services. Wireless devices may need to read the MCCH for several reasons such as: • Starting / ending a service; • Change the re-location information of the specific service; • Change the information of the S-CCPCH (code, TFCS) for the MTCH; • Change the radio bearer (RB) information for the MTCH; and • Begin counting / re-counting as defined by UMTS and described below. In one embodiment, the signaling information is sent according to a program in the MCCH. The MCCH program can be sent in an Emission Control Channel (BCCH) and made available for all wireless devices. In one modality, the MCCH program includes a repetition period, a modification period, and a period of access information, which are described in table 1.

TABLE 1 The MCCH program also identifies the specific frame or transmission time interval (TTI) that contains the beginning of an MCCH transmission. The same MCCH program can be used for all services to simplify both the transmission and reception of signaling information for services, as described below. Alternatively, different services or different groups of services can use different MCCH programs. The various parts of the MCCH program are described in more detail below. Table 2 lists several channels used to support broadcast and multicast services.

TABLE 2 The signaling information sent in the MCCH can be accommodated in two categories called critical signaling information and non-critical signaling information. The signaling information can be service-independent information and / or service-specific information. Critical signaling information includes signal information that is necessary to receive MBMS content for services. For example, the signaling information may include information from neighboring MBMS cells, MBMS service information, and MBMS radio bearer information. Non-critical signaling information includes all signaling information that is not critical signaling information. For example, non-critical signaling information may include MBMS access information. These various types of MBMS signaling information are described in a 3GPP TS document, 25,346, which is publicly available. Figure 3A shows a signaling transmission mode in the MCCH. The signaling information for each service is sent periodically in the MCCH in each repetition period to allow the wireless devices, which have just started monitoring the service, to receive the information. These wireless devices may have just been switched on, newly interested in the service, and / or just changed cells. For all of these scenarios (except possibly for the cell change scenario), wireless devices can tolerate relatively long delay in receiving signaling information. Therefore, the repetition period can become relatively long to reduce the signaling overload. In general, the repetition period can be any length of time and can cover any number of frames. The signaling information can be sent in the MCCH that starts in the first frame of each repetition period and for as many frames as necessary. Therefore, the repetition period identifies the beginning of an MCCH transmission. The duration of the transmission of the MCCH does not need to be specified and can be determined from a transport format combination indicator (TFCI) sent in the S-CCPCH. A wireless device can continue processing the S-CCPCH until the device determines that (1) all the MCCH information has been received, (2) a TTI that does not include MCCH data is received for the S-CCPCH, or (3) the signaling information received in the MCCH indicates that no additional reception of the MCCH is required (for example, if there are no changes in the MCCH). the signaling information for any of the desired services). The wireless device can stop processing the S-CCPCH for MCCH data when encountering any of the three conditions. The modification period can cover any number of repetition periods and represents the time in which the critical signaling information can be changed. In Figure 3A, different marks (eg, diagonal shading, gray shading and cross hatching) are used for the MCCH at different modification periods and represent potentially different signaling information that is being sent in the MCCH. The time that aligns the changes in the signaling information sent in the MCCH allows the wireless devices to know when it would be useful to read the MCCH. This time alignment also results in certain additional delays as well as certain restrictions in sending updated critical signaling information. Non-critical signaling information can be changed at any time, for example, in any repetition period. Figure 3B shows another mode of signaling transmission in the MCCH. The signaling information for each service is periodically sent to the MCCH in each repetition period, and the critical signaling information may be modified in each modification period, as described above for Figure 3A. At the beginning of each modification period, the system also transmits MBMS change information, which may include, for example, the identifiers of the services whose critical signaling information is modified in that modification period. Change information can be sent at least once in each modification period. The wireless devices can read the change information and can quickly determine if the device needs to read updated signaling information for any of the desired services. A notification mechanism is used to inform wireless devices about a near change in the critical signaling information sent in the MCCH. In one embodiment, the notification mechanism is executed using the MICH. The MICH carries notification indicators that launch the wireless devices interested in the services mapped to these indicators to read the MCCH for updated signage information. The notification indicators for all services can be sent in a way that is highly tolerant of channel errors. The MICH carries a single bit of information for each service, and wireless devices can not verify whether the information received in the MICH is correct (not CRC). Also, the MCCH is transmitted on the S-CCPCH using an unrecognized RLC (UM) mode, and the wireless device may miss one or even two MCCH transmissions before decoding correctly. The wireless device may have to wait for one or more repetition periods before it can decode the critical information, and after all the effort, the wireless device may discover that it was a false alarm. Reliable notification helps avoid unnecessary MCCH receptions. Second, notification indicators can be sent to the MICH in a way to allow wireless devices to detect notification indicators during their search occasions, which can reduce battery consumption. Notification indicators should also be sent so that wireless devices in various states related to MBMS can receive these indicators. These include wireless devices that await the arrival of a service, wireless devices that actively monitor a service but are interested in other services, and wireless devices that have just been turned on, or that have just moved from other cells or that are becoming interested in MBMS. Figure 4 shows a modality of transmissions in the MICH and MCCH. Each service is assigned a notification indicator in the MICH in each frame. In one embodiment, the notification indicator for each service is set to "1" throughout the modification period preceding a change in the critical signaling information for that service. Wireless devices can read the MICH in different frames (for example, on their search occasions) and may be aware of the need to read the MCCH in an asynchronous manner. The wireless devices are also aware of the MCCH program and are ready to begin receiving the MCCH at the start of the next modification period. It is not necessary for the timing of the notification indicators sent in the MICH to transmit any information regarding the timing of the MCCH, which is the case for the PICH and PCH because the timing of the PICH and PCH is related. Wireless devices that have detected the notification indicator for a desired service that is being established in a prior modification period, can read the MCCH at the beginning of the current modification period. Up-to-date signaling information can be retransmitted briefly (eg, immediately) after the first MCCH transmission in the current modification period, as shown in Figure 4. This rapid retransmission in the MCCH can improve reliability and guarantee that all or most wireless devices can receive the updated signaling information in the MCCH as soon as possible. Figure 5 shows exemplary transmissions in the PICH, MICH, MCCH and MTCH. The search indicators for each inert wireless device are sent in the PICH on the search occasions for the wireless device, as shown in the upper part of figure 5. The notification indicator for each service is sent in each frame in the wireless device. MICH and is set to the same notification value (either "1" or "0") for the entire modification period. The search indicator is set to "1" for the entire modification period immediately preceding a change in the critical signaling information for the service. The modification period is selected to be long enough so that all wireless devices (including wireless devices with the longest possible DRX cycle) can process the MICH and reliably detect at least one notification indicator for each desired service during the modification period. This allows most inert wireless devices to receive their search indicators as well as notification indicators for the desired services on their search occasions, which can reduce battery consumption. A wireless device with a DRX cycle that is shorter than the modification period can read the MICH during its search occasion in each DRX cycle. A wireless device with a DRX cycle that is longer than the modification period may awaken between its search occasions to read the notification indicators sent in the MICH. The modification period can be selected to be equal to or longer than a predetermined minimum duration (for example 2 seconds) so that wireless devices with long DRX cycles do not need to wake up too often. DRX cycles for wireless devices may also be limited to a predetermined maximum duration (eg, 5.12 seconds). Depending on how the DRX cycle and the modification period are configured, a wireless device can read one or multiple notification indicators for each desired service in each modification period. Each wireless device monitors the notification indicators in search of the desired services. When the wireless device detects the notification indicator for a desired service that is being established, the wireless device attempts to read the MCCH at the start of the next modification cycle to seek updated critical signaling information for that service. The wireless device reads the MCCH during all the time it takes to at least decode the MBMS change information. The wireless device also reads the MCCH during all the time it takes to at least decode the MCCH correctly, or until the continuous transmission in the MCCH is interrupted. The wireless device can detect the end of the MCCH transmission using the TFCI for the S-CCPCH, even if the device can not decode the S-CCPCH correctly. The wireless device may also terminate the processing of the MCCH if the MBMS change information indicates that there is no change in the critical signaling information for any of the desired services. Updates to the signaling information sent in the MCCH may reflect important changes in the MTCH such as, for example, reconfigurations of the S-CCPCH or MTCH. The updated signaling information may need to be applied synchronously on the transmitter and the receiver to ensure smooth reception of the content sent on the MTCH. In that case, the updated signaling information can be associated with an activation time. This activation time indicates when the signaling information will be applied. The activation time can be defined in relation to the start of the modification cycle and can be given in units of repetition cycles, frames, and so on. This allows the activation time to be transmitted in an efficient manner. The updated signaling information and its activation time can be sent some time before the activation time to allow the wireless devices enough time to receive and apply the signaling information. Figure 5 also shows an early retransmission in the MCCH immediately after the first transmission of the MCCH in the modification period to improve the reception of the updated signaling information. The first transmission of the MCCH and the early retransmission are associated with the same activation time that occurs after the end of the early re-transmission. Wireless devices that begin to monitor a given service between the time when the updated signaling information is sent in the MCCH and the activation time, will not be able to receive the services in progress. However, these wireless devices will be aware of the change of hindrance to the MTCH due to the activation time. Therefore, this length of time should not have a significant impact on performance as long as it is relatively short. As shown in Figures 3A to 5, the program for the MCCH has the following characteristics: • The signaling information is repeated in the MCCH based on a repetition period; • Changes in critical signaling information are not made in the middle of a modification period, which is multiple times the repetition period; • The notification indicators in the MICH are configured for the entire modification period preceding a change in the critical signaling information sent in the MCCH; • Wireless devices monitor the MICH at their convenience but ensure a good probability of detection within any modification period; and • When detecting that the notification indicator is set to the MICH, the wireless devices begin processing the MCCH in the next modification period until the updated signaling information in the MCCH is decoded correctly. UMTS uses a counting / re-counting procedure to determine the number of wireless devices that receive a particular MBMS service. The system can use this information to determine an optimal transmission mechanism for the service, for example, to decide whether to send the service using a point-to-point channel (ptp) or a point-to-multipoint channel (ptm) . A p-t-p channel can be more efficient if only a few wireless devices are receiving the service. A p-t-m channel can be more efficient if more wireless devices are receiving the service. The counting / re-counting procedure uses two parameters, a count flag and an access backward parameter. The count flag is a bit that indicates whether the count is enabled or disabled and can also be called a count indicator, a count indication, an access flag, and so on. The access backward parameter controls access to the system for the counting procedure. To enable the counting procedure for a given service, the system sets the counting flag for that service, which then requests that the inert wireless devices that receive that service establish a Radio Resource Control connection (RRC) with the system. The system periodically sends access information in the MCCH, which is used by the inert wireless devices to trigger the transmission of a signaling message, establishing the RRC connection if necessary. The access information includes the access backspace parameter and possibly other pertinent information. The access backward parameter defines a probability factor (PF), which indicates the probability with which wireless devices need to attempt an RRC connection procedure. The access backward parameter is used to control the load in the uplink due to the requests for the establishment of the RRC connection. This prevents a large number of wireless devices from being brought into connected RRC mode at the same time for counting purposes. Figure 6 shows exemplary transmissions in the MICH and MCCH for counting. The counting flag for the service is established whenever the counting is enabled for the service. The counting flag and access information can be sent to the MCCH periodically in each access information period. The access information period can be selected so that (1) information related to access (for example, the count flag and the backward parameter) is transmitted often enough to allow good control of access procedures and (2) wireless devices (including new wireless devices that began monitoring the system) may receive information related to access if they follow the MCCH program sent to the BCCH. The access information period can be an integer divisor of the repetition period to achieve the two aforementioned objectives, or can be defined as any length of time. The access information period program is part of the general transmission program of the MCCH, which is signaled in the BCCH. The mechanisms described above for sending notification indicators in the MICH and signaling information in the MCCH can also be used for the counting procedure. The counting flag can be set at the beginning of the modification period, which then limits the counting procedure to be initiated at the beginning of the modification period. This can simplify the counting procedure because all wireless devices begin the access procedure at the same time, which can reduce unpredictable randomness. In each access information period, the access information can be changed and / or the counting flag can be reset. This allows a quick control of the procedure of counting and establishment of the RRC connection. When a wireless device detects the counting flag set for a desired service, the device reads the access information and attempts to access the system using the access backward parameter included in the access information. From that point on, the wireless device attempts to read the MCCH in each access information period to determine the status of the count flag and obtain the latest access information. The wireless device updates the access backward parameter accordingly. The wireless device continues to read the MCCH according to the access information period until the counting flag is reset or the wireless device moves to an RRC state where counting is not required. Figure 7 shows a process 700 for transmitting the MICH, MCCH and MTCH by means of a base station in the system. A determination is made as to whether a new modification period has begun (block 712). If the answer is "yes", then the notification value for each service is determined based on whether the signaling information critical to the service will be modified in the next modification period (block 714). The notification indicator for each service is set throughout the current modification period to the notification value determined for that service (block 716). Updated signaling information (if any) is sent for each service and an early retransmission can also be sent (block 718). If the answer is "No" for block 712, then the process proceeds to block 722. For each service that is associated with an activation time for its updated signaling information, as determined in block 722, the information of Updated signage for that service is applied to the MTCH at the activation time (block 724). A determination is then made as to whether a new repetition period has begun (block 732). If the answer is "Yes", then the signaling information for each service is re-sent in the MCCH (block 734) at the time of activation (block 724). A determination is then made as to whether a new repetition period has begun (block 732). If the answer is "Yes", then the signaling information for each service is forwarded in the MCCH (block 734). Otherwise, the process proceeds to block 742. In block 742, a determination is made as to whether a new period of access information has begun. If the answer is "Yes", then the counting flag for each service remains configured to continue enabling the counting procedure or is reset to disable the counting procedure and then sent to the MCCH (block 744). The counting flag can be set at the beginning of the modification period and can be reset in any access information period. The current access information is also sent in the MCCH (block 746). If the answer is "No" for block 742 and also after block 746, the process returns to block 712. As described above, a base station transmits the signaling information for each service according to a program that includes, for example, a repetition period, a modification period, and an information period. of access. The modification period can be an integer multiple of the repetition period, and the access information period can be an integer divisor of the repetition period. The base station transmits the signaling information in each repetition period of a current modification period to allow wireless devices to quickly obtain this information. Any changes to the critical signaling information in the current modification period are transmitted at the beginning of the following modification period. If changes to the critical signaling information for a particular service are transmitted in the next modification period, then a notification indicator for the service is set for the entire current modification period to inform the wireless devices of the impending changes. Wireless devices can detect the notification indicator that is being established in the current modification period and can then retrieve the updated critical signaling information in the next modification period. As also described above, the base station can perform a counting procedure for a given service to count the number of wireless devices that receive the service and to determine the best transmission mechanism to be used for the service. The base station can establish a count flag for each service at the start of a modification period to enable counting for the service. The base station can send the counting flag for each service as well as access information in each access information period. If a wireless device detects that the counting flag is set for any service that is being received by the device, then the wireless device reads the access information and attempts to enter the system according to the access information. The access information can be changed and the counting flag can be reset in each access information period. Figure 8 shows a process 800 for receiving the MICH, MCCH and MTCH through a wireless device. The wireless device processes the MICH and detects the notification indicators for the desired services (block 812). A determination is then made as to whether the notification indicator is configured for some desired service (block 814).

If the answer is "Yes", then the wireless device processes the MCCH in the next modification period and obtains MBMS change information (block 816). The wireless device then reviews the change information to determine if the critical signaling information has changed for some desired service (block 818). If the critical signaling information is changed for some desired service, then the wireless device continues the MCCH process and reads the updated signaling information for each desired service identified by the change information (block 820). For each service that is associated with an activation time for the updated signaling information, as determined in block 822, the wireless device applies the updated signaling information for that service to the MTCH at the activation time (block 824) . The process ends after block 824 and also if the answer is "No" for block 814, 818 or 822. Figure 9 shows a process 900 for counting by the wireless device. The wireless device reads the count flag for each desired service, for example, at the start of the modification period (block 912). A determination is then made as to whether the counting flag is set for some desired service (block 914). If the answer is "Yes", then the wireless device obtains the access information in the MCCH (block 916) and tries to establish an RRC connection according to the access information (block 918). Subsequently, for each access information period service, as determined in block 920, the wireless device reads the count flag, reads the access information in the MCCH, and attempts to enter the system based on the parameter of current access recoil (block 922). The wireless device continues reading the count flag and attempts to access the system until the counting flag is reset (block 924) or the wireless device has been moved to an RRC state where counting is not required (block 926). The count for an ongoing service (which is called re-counting) can be performed in the manner described above in Figure 9 for counting at the start of a service. In general, several mechanisms can be used to send notifications for signaling information sent in the MCCH and notifications for the counting procedure. These notifications can be sent (1) in the MICH, as described above, (2) in the S-CCPCH that carries the MTCH, or (3) using dedicated search. A notification may be sent in-band on the S-CCPCH to notify wireless devices of a re-configuration during an ongoing session (for example, due to the introduction of another service in the same S-CCPCH). The S-CCPCH can be received by wireless devices that actively monitor a service. Sending the in-band notification in the S-CCPCH allows the transmission of additional information along with the notification, such as the actual service ID and / or an activation time. In-band signaling has a low probability of false alarm at the cost of additional overhead. The dedicated search is generally applicable to wireless devices that have established RRC connections. The transmission of notifications in the MICH and the signaling information in the MCCH, as shown in Figures 3A to 5, can provide several advantages such as: • Simplifying the execution of the wireless device because the wireless devices know a priori, based on the MCCH program, how long the notification will be sent to the MICH and when it would be useful to read the MCCH; • Allow all or most wireless devices to start listening to the MCCH at the same time, which shortens the delay to receive the updated MCCH information, allows activation time to be set near the limit of the modification period, allows the -transmissions tighter especially when the MCCH information is modified, and eliminates the need to send old and new configuration information at the same time; and • Can be used for all notification scenarios in MBMS and for the wireless device in all states (inert and connected). Wireless devices can read the MICH periodically during its search occasions (if the devices are inert) or continuously during the reception of the MTCH (if the devices are connected).

The notification indicators sent in the MICH potentially have a higher false alarm probability than the in-band notification, but this false alarm probability can be reduced by reading the notification indicators more frequently during the modification period. The additional delay to change the critical signaling information can be improved by selecting a convenient modification period. The notification scheme described here can be used as the main notification mechanism to indicate the start of the service and for the counting procedure. This notification scheme can also be used to send notifications during ongoing transmissions. Figure 10 shows a block diagram of a modality of a base station 11Ox and a wireless device 120x. For the downlink, at the base station 11Ox, an encoder 1010 receives traffic data for wireless devices and services, signaling information, and other types of data. The encoder 1010 processes (eg, encodes, interspersed and maps into symbols) the traffic and signaling data and generates modulation symbols. A modulator 1012 performs channeling, spectral spreading, encryption, and so on, on modulation symbols for several physical channels (eg, PICH, MICH, and S-CCPCH) and provides a stream of data chips. A transmitter unit (TMTR) 1014 conditions (for example, converts to analog, amplifies, filters and overconverts in frequency) the data chips and generates a downlink signal, which is transmitted through an antenna 1016. In the device 120x wireless, a 1052 antenna receives the downlink signal from the base station 11Ox and provides a received signal to a receiver unit (RCVR) 1054. The receiving unit 1054 conditions (e.g., filters, amplifies and subverts frequency) the received signal, digitizes the conditioned signal, and provides data samples. A demodulator (Demod) 1056 processes the data samples and provides estimates of symbols. The demodulator 1056 further performs the detection of notification indicators, search indicators, and count flags, as ordered by a controller 1060. A decoder 1058 processes (e.g., desmaps, deinterleaves, and decodes) the symbol estimates and provides decoded data for the traffic data transmitted and signaling sent by the base station llOx. In the uplink, in the wireless device 120x, the traffic data is processed by an encoder 1070, further processed by a modulator 1072, and conditioned by a transmitter unit 1074 to generate an uplink signal, which is transmitted through of the antenna 1052. In the base station 11Ox, the uplink signal is received by the • antenna 1016, conditioned by receiver unit 1030, processed by a demodulator 1032 and further processed by a decoder 1034. Controllers 1020 and 1060 direct the operation at the base station 11Ox and the wireless device 120x, respectively. The controllers 1020 and 1060 can also perform various functions for transmission and reception, respectively of notification indicators and signaling information for the services. For example, the controller 1020 may perform the process 700 in FIG. 7 for the transmission of signaling information. The controller 1060 may perform the process 800 in FIG. 8 for reception of signaling information and the process 900 in FIG. 9 for the counting procedure. The memory units 1022 and 1062 store data and program codes for the controllers 1020 and 1060, respectively. A timer 1024 provides time information for the controller 1020, which uses the time information to maintain the MCCH program. A timer 1064 provides time information for the 1060 controller, which uses the time information to determine when to wake up to process the PICH and MICH as well as maintain the MCCH program. The signaling transmission techniques described herein can be executed through various means. For example, these techniques can be executed in hardware, software or a combination of both. For a hardware execution, the processing units used to transmit signaling information may be executed within one or more specific application integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD) , programmable logic devices (PLD), field-programmable gate arrays (FPGA), processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. The processing units used to receive the signaling information may be executed within one or more ASICs, DSPs, and so on. For a software execution, the signaling transmission techniques can be executed with modules (for example, procedures, functions, and so on) performing the functions described herein. The software codes may be stored in a memory unit (e.g., memory unit 1022 or 1062 in FIG. 10) and executed by means of a processor (e.g., controller 1020 or 1060). The memory unit can be executed inside the processor or outside the processor, in which case it can be communicatively coupled to the processor through various means, as is known in the art. The prior description of the described embodiments is provided to enable those skilled in the art to make or use the present invention. Various modifications to these modalities 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. Therefore, the present invention is not intended to be limited to the embodiments shown herein but will be accorded the broadest scope consistent with the principles and novel features described in the present invention.

Claims (44)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as a priority: CLAIMS

1. - A method in a communication system, comprising: transmitting signaling information for at least one service in each of a plurality of repetition periods of a current modification period, the signaling information is composed of critical signaling information and non-critical signaling information; and transmitting changes to the critical signaling information at least for a service that starts in a subsequent modification period.

2. - The method according to claim 1, further comprising: retransmitting the signaling information for at least one service after a first transmission of the signaling information in a first repetition period and before a second period of repetition in the current modification period.

3. The method according to claim 1, further comprising: setting a notification indicator for each service to a predetermined value in the current modification period if changes to the critical signaling information for the service are transmitted in the following modification period.

4. - The method according to claim 3, further comprising: transmitting the notification indicator for each service in each frame in the current modification period.

5. - The method according to claim 1, further comprising: transmitting change information for at least one repetition period of the current modification period, the change information for the current modification period identifies each service with changes for the critical signaling information in the current modification period.

6. The method according to claim 1, further comprising: sending an activation time for each selected service with changes in the critical signaling information; and apply the changes in the critical signaling information for each selected service at the time of activation for the selected service.

7. - The method according to claim 1, further comprising: transmitting a program with the repetition period and the modification period.

8. - The method according to claim 1, further comprising: defining the modification period to be an integer multiple of the repetition period.

9. - The method according to claim 1, further comprising: defining the modification period to be iqual or longer than a predetermined minimum duration.

10. An apparatus in a communication system, comprising: a transmitting unit operative for transmitting signaling information for at least one service in each of a plurality of repetition periods of a current modification period and transmitting changes to the critical signaling information for at least one service initiating in a subsequent modification period, signaling information is composed of critical signaling information and non-critical signaling information; and an operating controller for directing the transmission of signaling information by means of the transmitter unit.

11. The apparatus according to claim 10, characterized in that the controller further operates to set a notification indicator for each service to a predetermined value in the current modification period, if changes are transmitted to the critical signaling information for the service in the next modification period.

12. The apparatus according to claim 10, characterized in that the transmitting unit further operates to transmit change information for at least one repetition period of the current modification period., the change information for the current modification period identifies each service with changes for the critical signaling information in the current modification period.

13. The apparatus according to claim 10, characterized in that the transmitting unit further operates to send an activation time for each selected service with changes in the critical signaling information, and wherein the controller further operates to apply the changes in the critical signaling information 'for each service selected at the time of activation for the selected service.

14. The apparatus according to claim 10, characterized in that the transmitting unit further operates to transmit a program with the repetition period and the modification period.

15. An apparatus in a communication system, comprising: means for transmitting signaling information for at least one service in each of a plurality of repetition periods of a current modification period, the signaling information is composed of critical signaling information and non-critical signaling information; and means for transmitting changes to critical signaling information for at least one service that starts in a subsequent modification period.

16. The apparatus according to claim 15, further comprising: means for setting a notification indicator for each service to a predetermined value in the current modification period if changes to the critical signaling information for the service are transmitted in the next modification period.

17. The apparatus according to claim 15, further comprising: means for transmitting change information for at least one repetition period of the current modification period, the change information for the current modification period identifies each service with changes for critical signaling information in the current modification period.

18. The apparatus according to claim 15, further comprising: means for sending an activation time for each selected service with changes in the critical signaling information; and means for applying the changes in the critical signaling information for each selected service at the time of activation for the selected service.

19. The apparatus according to claim 15, further comprising: means for transmitting a program with the repetition period and the modification period.

20. A method in a communication system, comprising: establishing at least one counting flag for at least one service in a current modification period, the counting flag for each service is established at the beginning of the modification period current if the count is enabled for service; and transmitting access information in each of a plurality of access information periods in the current modification period, the access information includes at least one count flag and access information used to enter the system for counting.

21. The method according to claim 20, further comprising: changing the access information, if applicable, in each period of access information.

22. The method according to claim 20, further comprising: resetting the count flag for each service, if applicable, in any access information period.

23. The method according to claim 20, further comprising: defining the period of access information to be an integer divisor of the modification period.

24. An apparatus in a communication system, comprising: means for establishing at least one counting flag for at least one service in a current modification period, the counting flag for each service is established at the beginning of the period of current modification if the count is enabled for service; and means for transmitting access information in each of a plurality of access information periods in the current modification period, the access information includes at least one count flag and access information used to enter the system for counting.

25. The apparatus according to claim 24, further comprising: means for changing the access information, if applicable, in each period of access information.

26. The apparatus according to claim 24, further comprising: means for resetting the count flag for each service, if applicable, in any period of access information. 27.- A method in a communication system, comprising: detecting at least one notification indicator for at least one service in a first modification period, the notification indicator for each service is established in the first modification period if critical signaling information is changed for the service in a second modification period after the first modification period; and receiving, in the second modification period, the critical signaling information for each service having the notification indicator configured in the first modification period. 28. The method according to claim 27, further comprising: determining whether the critical signaling information for any service is associated with an activation time; and apply the critical signaling information for each service at the time of activation, if present. 29. The method according to claim 27, further comprising: receiving change information identifying each service with changes for the critical signaling information in the second modification period; and receive critical signaling information for each service, at least among a service, identified by the change information. The method according to claim 27, further comprising: arousing on the search occasions assigned to a wireless device; and detecting a search indicator for the wireless device at each search occasion, and wherein at least one notification indicator for at least one service is detected at each search occasion for the wireless device. 31.- An apparatus in a communication system, comprising: a demodulator operating to detect at least one notification indicator for at least one service in a first modification period, the notification indicator for each service is established in the first modification period if critical signaling information is changed for the service in a second modification period after the first modification period; and a processor operating to receive, in the second modification period, critical signaling information for each service having the notification indicator configured in the first modification period. 32. The apparatus according to claim 31, further comprising: a controller that operates to determine if the critical signaling information for any service is associated with an activation time and to apply the critical signaling information for each service in the activation time, if present. 33.- The apparatus according to claim 31, characterized in that the processor operates to receive change information that 'identifies each service with changes for the critical signaling information in the second modification period and to receive the critical signaling information for each service, at least among a service, identified by the change information. 34. The apparatus according to claim 31, further comprising: a timer that operates to indicate the search times assigned to the apparatus, and wherein the demodulator operates to detect a location indicator for the wireless device and to detect, at least one for a notification indicator, at least one service on each search occasion for the wireless device. 35.- An apparatus in a communication system, comprising: means for detecting at least one notification indicator for at least one service in a first modification period, the notification indicator for each service is established in the first period modification if critical signaling information is changed for the service in a second modification period after the first modification period; and means for receiving, in the second modification period, the critical signaling information for each service having the notification indicator configured in the first modification period. 36. The apparatus according to claim 35, further comprising: means for determining whether the critical signaling information for any service is associated with an activation time; and means for applying the critical signaling information for each service at the time of activation, if present. The apparatus according to claim 35, further comprising: means for receiving change information identifying each service with changes for the critical signaling information in the second modification period; and means for receiving critical signaling information for each service, at least among a service, identified by the change information. 38.- The apparatus according to claim 35, further comprising: means for awakening in the search occasions assigned to the apparatus; and means for detecting a search indicator for the apparatus and at least the notification indicator for at least one service on each search occasion for the apparatus. 39.- A method in a communication system, comprising: detecting at least one flag for at least one service in a current modification period, the counting flag for each service is established at the beginning of the modification period current if the count is enabled for the service; and if the counting flag is established for any one of at least one service, receive access information, and try to enter the system, according to the access information received. The method according to claim 39, further comprising: for each period of access information in the current modification period, detecting for the count flag for each service with the count flag established at the beginning of the modification period Current, and if the counting flag is still established in the access information period for any at least one service, receive access information, and try to enter the system, according to the access information received. 41. The method according to claim 39, further comprising: terminating system access if at least one counting flag is reset for at least one service. 42. The method according to claim 39, which further comprises: terminating system access if a connection is established with the system. 43.- An apparatus in a communication system, comprising: means for detecting at least one counting flag for at least one service in a current modification period, the counting flag for each service is established at the beginning of the period of current modification if the count is enabled for the service means to receive access information if the count flag is configured for any at least one service; and means to try to enter the system, according to the access information received, if the counting flag is established for any one of at least one service. The apparatus according to claim 43, further comprising: means for detecting, in each access information period in the current modification period, the counting flag for each service, wherein the counting flag is established at the beginning of the current modification period; means for receiving access information if the counting flag is still configured in the access information period for any one of at least one service; and means to attempt to enter the system, according to the access information received, if the counting flag is still established in the access information period for any one of at least one service.