MXPA06009218A - Transmission of notifications for broadcast and multicast services - Google Patents

Abstract

To transmit notification indicators for broadcast and multicast services, a base station maps the services to random sequences based on their identifiers. The base station generates the random sequence for each service based on a hash function or a PN generator and the service identifier. Each random sequence is associated with a specific location for sending a notification indicator in each frame. The locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence. This randomness characteristic reduces the likelihood of false alarm. For each service, the base station sets the notification indicators to the same notification value in each modification period. The base station transmits the notification indicators for each service at the random locations determined by the random sequence for the service.

Description

TRANSFER OF NOTIFICATIONS FOR DISTRIBUTION AND MULTI-DIFFUSION SERVICES I. Field of the Invention The present invention relates generally to communication, and more specifically to techniques for transmitting and receiving notifications for broadcast and multicast service in a communication system.

II Background of the Invention A communication system can provide single broadcast, multicast and / or broadcast services. A single broadcast service provides point-to-point communication between at least one base station and a specific wireless device. A multicast service provides point or multipoint communication between at least one base station and a group of wireless devices. The broadcast services provide point-to-multipoint communication between at least one base station and all wireless devices within a designated broadcast area. Some of the examples of multicast and broadcast services include news and data services, subscription-based services, push-to-talk, etc. Multicast and broadcast services can send data to wireless devices sporadically, periodically or continuously. The communication system may need to send signaling (eg, control information, configuration information, etc.) for the broadcast and multicast services supported by the system. This signaling can be sent on a control channel. A wireless device that receives one or more services can then monitor the control channel for the signaling sent for the service (s) that are received. The wireless device can operate in an inactive state as long as it is not actively exchanging data with one or more base stations in the system. In the idle state, the wireless device is periodically activated to receive search messages and overload messages from the system and turn off the circuitry as much as possible in the remaining time in order to save battery power. It is highly desirable for the wireless device, which while active, to be informed in some way of any signaling that is sent in the control channel for the service (s) being received. The wireless device may then be able to receive relevant messages for itself and signaling for the service (s) that are received without spending too much battery power.

Therefore, there is a need in the art for techniques for sending notifications for signaling sent for broadcast and multicast services.

SUMMARY OF THE INVENTION Techniques for transmitting and receiving notification indicators for broadcasting and multicasting services in a communication system are described herein. A base station maps the services into random sequences, a random sequence for each service, based on identifiers for the services. The base station generates the random sequence for each service based on a unilateral function or a pseudo-random number (PN) generator and the service identifier. Regardless of how the random sequence is generated, each random sequence is associated with a specific location to send a notification indicator in each frame. The locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence. This randomization feature reduces the probability of false alarm as described in the following. For each service, the base station establishes the notification indicators at the same notification value in each modification period, which may be of any length of time. The base station transmits the notification indicators for each service in an MBMS Indicator Channel (MICH) at the random locations determined by the random sequence for that service. The base station also transmits search indicators for each inactive wireless device in a Search Indicator Channel (PICH) in frames assigned to the wireless device and in locations determined by a PICH sequence for the wireless device. To receive notification indicators for at least one desired service, a wireless device determines the random sequence for each desired service. The wireless device also determines the frames in which they receive their search indicators. For each of these "active" frames the wireless device receives (1) the notification indicator for each service at the location in the MICH determined by the random sequence for the service and (2) the search indicator for the wireless device at the PICH location determined by the PICH sequence. The wireless device determines the notification value for each service in each modification period based on all notification indicators received for that service in that modification period. Various aspects and embodiments of the invention are described in further detail in the following.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows a wireless communication system. FIGURE 2A shows the PICH format of the Universal Mobile Communication System (UMTS). FIGURE 2B shows a format of a PICH frame. FIGURE 3 shows exemplary transmissions in the PICH, MICH, MCCH and MTCH in UMTS. FIGURE 4 shows two random sequences with random locations for notification indicators. FIGURE 5 shows a process consisting of a base station for transmitting notification indicators for broadcast and multicast services supported by the base station. FIGURE 6 shows a process performed by a wireless device to receive notification indicators for at least one service. FIGURE 7 shows a block diagram of the base station and the wireless device.

DETAILED DESCRIPTION OF THE INVENTION The word "exemplary" is used herein to mean that "it serves as an example, case or illustration." Any mode described herein as an example does not necessarily have to be interpreted as preferred or advantageous over other modalities. FIGURE 1 shows a wireless communication system 100 capable of supporting multimedia broadcast and multicast services. System 100 includes base stations 110 that communicate with wireless devices 120. For simplicity, only the 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 called 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 called a user equipment (UE), a mobile station, a terminal or some other terminology. A radio network controller (RNC) 130 is coupled to the base stations 110 and provides coordination and control for these base stations. The RNC 130 can also be called a base station controller (BSC) or some other terminology. A core network 132 (C?) Is coupled to R? C 130 and other systems and networks, such as a telephone network switched by (PSTN), a packet switched data network, etc. The core network 132 interconnects the system 100 with these other systems and networks. The system 100 can be an Access system Multiple Division by Code (CDMA), Time Division Multiple Access (TDMA) system, a Division Multiple Frequency Access (FDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system or some other multiple access system. A CDMA system can implement one or more CDMA radio access technologies (RAT) such as Broadband CDMA (W-CDMA) and cdma2000. cdma2000 covers the IS-2000, IS-856, and IS-95 standards. A TDMA system can implement one or more TDMA RATs, such as the 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 GSM as RAT and is described in documents of a consortium called "3rd Generation Partnership Project" (3GPP). The cdma2000 is described in documents from a consortium called "3rd Generation Partnership Project 2 (3GPP2) .The 3GPP and 3GPP2 documents are publicly available." For clarity, the techniques of transmitting and receiving notification are specifically described in the following for UMTS These techniques can be used for multicast-broadcast multimedia (MBMS) services in UMTS., a Search Indicator Channel (PICH) is used to send search indicators for inactive wireless devices. An inactive wireless device is a wireless device that has registered with the system and is operating in an idle mode or a PCH mode. Search indicators for each inactive wireless device indicate whether messages are being sent in a Search Channel (PCH) for wireless device. The PCH is a transport channel that is carried in a Physical Channel of Secondary Common Control (S-CCPCH). Each inactive wireless device monitors the PICH for 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. A key characteristic of the indicator channels such as PICH and MICH is that the inftion carried in these channels is short and without code and in this way they are received and interpreted very quickly. FIGURE 2A shows the PICH ft in UMTS. The PICH is divided into frames, with each frame having a duration of 10 milliseconds (ms). Each frame is identified by a 12-bit system frame number (SFN) that is transmitted simultaneously in a Primary CCPCH (P-CCPCH). The SFN is reset to 0 at a specific time, incremented by one for each frame after it, and returns to zero after reaching the maximum value of 4095. Each inactive wireless device is assigned on search occasions that are specific frames in the which the wireless device can receive its search indicators. The search occasions for each wireless device are separated by a time interval called the DRX cycle (discontinuous reception mode). The DRX cycle can be configured for each wireless device and typically is 1.28 seconds. In general, the DRX cycle can vary 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 that include an International Mobile Subscriber Identifier (IMSI), which is an identifier that is unique to each wireless device. Different wireless devices with different IMSI can be assigned in different search occasions even if they have the same DRX cycle. The DRX cycles and frames for UMTS correspond to slot and slot cycles, respectively, and in some of the systems that support slotted mode search. FIGURE 2B shows the ft of a frame for PICH. Each PICH frame includes 300 bits, which are labeled as bits b0 to b299. The first 288 bits are used for the Np search indicators, and the last 12 bits are reserved for other uses. The number of search indicators (Np) in each PICH frame can be configured by the system and can take a value of 18, 36, 72 or 144. Each search indicator is sent in 288 / Np consecutive bits in the frame of PICH, where 288 / Np can take a value of 16, 8, 4 or 2. The 288 / Np bits are all set to * 1 'if the search indicator equals "1" and is set to "0" and the search indicator is equal to 0 The search indicators Np are sent in locations of the search indicator Np that are numbered from 0 to Np-1 (not shown in FIGURE 2B) Each inactive wireless device that is associated with an indicator Search on each search occasion The search indicator for each wireless device is sent at a location that is determined as follows: Where SFN is the system frame number for the search occasion; Pl- (IMSI div 8192) mod Np; LxJ is a floor operator that provides the next value of the lower whole number for x; mod denotes an operation of the module; and qp is the location of the search indicator within the search occasion. As shown in equation (1), the location of the search indicator for a given wireless device changes between possible locations Np based on the SFN of the search occasion. Thus, depending on the SFN of the search occasion, the wireless device may need to process a different location to obtain its search indicator. Equation (1) also indicates that up to nP non-overlapping sequences of search indicators (or PICH sequences) can be formed. Each PICH sequence is associated with a different value of Pl, which can vary from 0 to Np-1 due to the operation of the module-Np to calculate Pl. Each PICH sequence is associated with a specific location to send the search indicator in each frame (or each SFN). The Np PICH sequences are not overlapping since neither of the two PICH sequences uses the same location of the search indicator in any frame. In fact, the (Np-1) of PICH for PI = 1 to Np-1 are only different versions changed (by the module-Np) of the sequence of PICH for PI = 0. Two wireless devices can map the same value of Pl based on their IMSI. These two wireless devices can then have the same PICH sequence, and their search indicator locations can overlap in each frame. If these two wireless devices also have the same search occasions, then their search indicators can be sent in the same frames and in the same location in each frame. If multiple search indicators are mapped to the same location, then a value of l 'is sent to the location if any of those search indicators equals' l ', and a value of 0' is sent to the location if all the search indicators are equal to? 0 For two wireless devices with the same PICH sequence and search occasions, whenever a search indicator is set for a wireless device, the other wireless device can also detect (possibly erroneously) this search indicator and can process the PCH to search for search messages. In UMTS, an MBMS Indicator Channel (MICH) is used to send the MBMS notification indicators (or simply, notification indicators) that indicate if the messages are being sent in a Control Channel of Point or Multipoint of MBMS (MCCH). The MCCH is a transport channel that is also carried in the S-CCPCH. Messages sent in the MCCH contain information that allows wireless devices to receive a Point-to-Multipoint MBMS Traffic Channel (MTCH). Such information can indicate, for example, what services are active, how to decode the MTCH, if the temporary combination is possible, etc. The MTCH is a transport channel that carries traffic data or content 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 as bits b0 through b299. The first 288 bits are used for the Nn notification indicators, and the last 12 bits are reserved. The number of notification indicators (Nn) in each MICH frame can be configured by the system and can take a value of 18, 36, 72 or 144. Each notification indicator is sent in 288 / Nn consecutive bits in the frame of MICH, where 288 / Nn can take a value of 16, 8, 4 or 2. The Nn notification indicators are sent in the Nn locations of the indicator that are numbered from 0 to Nn-1. The notification indicators can also be sent using the last 12 bits in each PICH frame. Each broadcast / broadcast service is assigned specific notification indicators, which are set in l 'whenever a message is 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"). As long as the notification indicator for any desired service is stable, the wireless device also processes the S-CCPCH to look for messages sent for the service. The notification indicators for all the services supported by the system (or "supported services") must be sent to the MICH in a way to achieve the following goals: • Minimize the activation time and, therefore, the energy consumption, for each inactive wireless device to receive its search indicator and notification indicators for all desired services during each activation period; • Minimize the false alarm caused by overlapping notification indicators for different services; and • Minimize the presence of transmission used for the notification indicators for all supported services. For the PICH, a false alarm occurs whenever a wireless device erroneously detects a search indicator that is set for another wireless device as being set for itself. For the MICH, a false alarm occurs whenever a wireless device mistakenly detects a notification indicator that is stable for an unwanted service as being established for a desired service. In any case, a false alarm causes the wireless device to process the PCH or MCCH for messages that can not be applied to the wireless device, which consumes battery power and shortens the waiting time. False alarms can not be avoided for the PICH if there are more inactive wireless devices than the number of search indicator locations available, and the search indicators for multiple wireless devices map and overlap in the same location. However, false alarms for the PICH do not adversely impact performance for several reasons. First each wireless device typically receives only a small search number, so the search indicators for each wireless device are set infrequently and the number of false alarms is small. Second, not all wireless devices map the same sequence of PICH have overlapping search indicators from their search occasions, which constitutes an additional dimension by which to distinguish between wireless devices, may be different. Third, wireless devices typically need to detect their search indicators as quickly as possible and often use an aggressive detection algorithm that can falsely declare a search indicator as being established when this is not the case. Fourth, because PICH is not only monitored by inactive wireless devices, a false PICH alarm only impacts battery life but does not adversely impact service reception. False alarms are also unavoidable for the MICH if the number of supported services exceeds the number of reported notification indicator locations, however, false alarms for the MICH may be more harmful than false alarms for the PICH. For a wireless device that is not yet receiving a service, the impact of the false alarms for the MICH may be some additional battery power consumption. 0 by a wireless device, which is already receiving a service and is not capable of concurrently receiving the MCCH and the MTCH, a false alarm causes the wireless device to process the MCCH instead of the MTCH and result in data loss to the MTCH. To achieve a first goal observed in the above for the notification indicators, each service can be assigned a notification indicator in each frame. If a message is to be sent to the MCCH for the service, then the notification indicators for the service are set to? L 'for a period long enough so that even a wireless device with the longest possible DRX cycle is able to receive the notification indicator with good detection probability. FIGURE 3 shows exemplary transmissions in the PICH, MICH, MCCH and MTCH. The search indicators for each inactive wireless device are sent in the PICH on search occasions for the wireless device, as shown at the top of FIGURE 3. The notification indicators for each service are sent in each frame of the MICH and are set to the same notification value, (either in 11 'or? 0') for the entire modification period. The modification period may represent a time interval in which the "critical" signaling information, which is the information that is needed to receive the MBMS content, may be changed. In general, signaling information can be service-independent information and / or service-specific information. The notification period is selected to be long enough so that all wireless devices can reliably detect at least one notification indicator sent to the MICH during the modification period. 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 larger than the modification period can be activated between search occasions to read the MICH. The modification period can be selected to be equal to or greater than a predetermined minimum duration (for example, 2 seconds) so that wireless devices with long DRX cycles do not need to be activated very frequently. Depending on how the DRX cycle and the modification period are configured, a wireless device may be able to read one or multiple notification indicators for each desired service in each modification period. If the change indicators for all supported services are sent in each MICH frame, then the single dimension capacity level is number of indicator locations (Nn) within a MICH frame. If equation (1) is used to determine the location of the notification indicator for each service in each frame, then the notification indicators for either of the two services that have the same value of Pl may overlap in each frame. False alarms for the MICH can then be mastered by overlapping notification indicators for different services. If a notification is sent for a service, then all wireless devices interested in any of the other services mapped in the same PICH sequence defined by equation (1) may erroneously detect this notification and may also process the MCCH. This can result in a high false alarm probability for the MICH, which is undesirable. To reduce the probability of false alarm for the MICH, a large number of sequence of notification indicators (or random sequences) can be formed by randomizing the indications of the notification indicators for these random sequences. This randomization can be achieved in several ways, for example, by using a unilateral function, a PN generator, etc. For clarity, several schemes for generating the random sequences are described in the following. In a first randomization scheme, the random sequences are formed based on a unilateral function that maps each random sequence into a random location in each frame based on an identifier for the random sequence. Each random sequence is associated with a different NI value that can vary from 0 to G-1, where G is a parameter that determines the number of random possible sequences. For each random sequence, the location of the notification indicator in each frame can be determined as follows: Nn? * _ =. { [Cx (NI® ((C xSFN) modG))] modG} x- Eq. (2) G where C is a constant that is described in the following; T indicates an exclusive operation OR (XOR) type bit; and gpi is the location of the notification indicator within the frame. The G parameter can be selected as a relatively large power of two and can also be based on an exchange between computational complexity and the probability of default conditions between the notification indicators for the different services. The default conditions mean that random sequences always share the same locations for their notification indicators. In one embodiment, G is selected as G = 21S, NI is a 16-bit value, and there are 21S possible random sequences. The constant C can be defined, for example, as follows: In general, the constant C can be defined so that C and G are prime numbers with each other. Each service is identified by a service identifier, which can be an Identity of the Temporary Mobile Group (TMGI). Services in this way can only be identified by their TMGIs in the same way that wireless devices can only be identified by their IMSI. Each service can be mapped to a specific NI value based on its TMGI, for example, as follows: In general, each service can be mapped to a specific NI value based on any function of the service identifier. For example, the mapping can be based on a function f (x) = mod G, where x is the service identifier and f (x) is the value NI. Other functions can also be used to map service identifiers to NI values. The unilateral function shown in equation (2) randomizes an SFN function with a function of the service identifier (or NI) to ensure that different services are associated with different random locations for their notification indicators in different frames. The use of C and G in the unilateral function ensures that all indicator locations within each frame will equally likely be assigned for each service. From a complexity point of view, the one-sided function in equation (2) has an advantage that can be calculated directly based on SFN and NI values and does not require timing a PN generator for each frame in which the device Wireless is inactive. Each value of qn ± can be calculated with three multiplications, an XOR operation, and some truncations for module operations. In a second randomization scheme, the 2 * 2 PICH Each random sequence is associated with a different NI value that can vary from 0 to G-1. For each random sequence, the location of the notification indicator of each frame can be determined as follows: where qn2 is the location of the notification indicator within the frame. The unilateral function shown in equation (5) also randomizes an SFN function with a function of the service identifier to ensure that different services are mapped in different locations for their notification indicators in different frames. The one-sided function shown in equation (5) uses a function different from SFN than the one-sided function shown in equation (2). Each value of qn2 can be calculated with four additions, two multiplications and some truncations. In a third randomization scheme, the random sequences are formed based on a PN generator that selects different locations of the random indicator in different frames for each random sequence. The selection of the random locations of the indicator can be achieved in several ways. For clarity, a specific modality is described in the following. For this mode, the PN generator is implemented with a 16-bit linear feedback shift register (LFSR) that implements a selected generator polynomial. This generator polynomial can be, for example, xLS + xL2 + x3 + x + l. The implementation of the linear feedback shift register is known in the art and is not described herein. The shift register is reset to a predetermined non-zero value whenever SFN is returned to zero (or rolled over). The content of the shift register at any time is not specific to any wireless device or any service. Each base station can maintain a generator in this way D.E.P? for all supported services. Each random sequence (and thus each service) is associated with a different value? I that can be vary from 0 to G-l. For each random sequence, the location of the notification indicator in each frame can determine as follows: ? p? p3 = rx- G Eq. (6) where r is a binary number of 16 bits intermediate generated by the generator of P ?; Y gp3 is the location of the notification indicator inside the plot. Equation (6) indicates that the constant C, which is used for the unilateral functions in equations (2) and (5), is not needed for the third randomization scheme.

Each bit of the 16-bit binary number r can be determined in the state of the shift register and the value NI for the random sequence. Each bit i of the number r can be determined, for example, to perform the following operations: 1. Time the PN generator once to update the content of the shift register. 2. perform G an AND type bit operation between the updated content of the shift register and the value NI to generate a number of bits. 3. perform a sum of modulo 2 on all 16 bits of the number s to obtain a binary value for bit i of the number r. The set of operations described in the above is performed 16 times, one for each of the 16 bits of the number r. The shift register in this mode is clocked 16 times for each frame. The generator PN is also clocked for each frame in which the wireless device is inactive so that the PN generator is in the proper state. A single PN generator can be used to generate all of the random sequences G. For the modality described above, the random sequences have a length of 4096 frames due to the use of a 16-bit linear feedback shift register for the generator. PN and the timing of the PN generator 16 times per frame. Random sequences of longer or shorter lengths can be obtained by using PN generators with more or fewer bits. The length of the random sequences must be at least as large as the longest possible modification period. In another embodiment of the third randomization scheme, different random sequences are associated with different initial values for the linear feedback shift register. These random sequences are thus mapped to different positions in a PN sequence generated by the PN generator. Each random sequence can be generated, for example, by initializing the PN generator with the associated initial value (for example, provided that SFN returns to zero), timing the PN generator once for each frame, and performing a module operation. Nn in the content of the shift register to obtain the location of the indicator for the frame. For this mode, a PN generator is maintained for each random sequence to be generated. In yet another mode, each random sequence can be generated by resetting the PN generator (for example, at a predetermined value, as long as the SFN returns to zero), timing the PN generator once per frame, by performing an exclusive OR of the content of the shift register with a masking value for the random sequence, and perform a modulo-Nn operation on the result of the exclusive OR operation to obtain the location of the indicator for the frame. For this modality, different random sequences are associated with different masking values, and a single PN generator can be used to generate all the random sequences. Random sequences can also be generated in other ways using the PN generator. FIGURE 4 shows the two random sequences X and Y with random locations for the notification indicators. These two random sequences can be generated using a unilateral function or a PN generator. The random X sequence is generated with an NI value of X, and the random sequence Y is generated with a value NI of Y, where X and Y can each be any value within the range of 0 to G-1. For simplicity, FIGURE 4 shows a case where Nn = 8, and there are 8 indicator locations in each frame. For each random sequence, the notification indicator is sent in a random location in each frame. For the example shown in FIGURE 4, the random sequences X and Y adjoin and their notification indicators overlap in a single frame n and no other frame shown in FIGURE. If the notification indicators for only a random sequence are set to Y, then a wireless device may encounter a false alarm if it reads only the notification indicator sent in frame n. The wireless device may not find a false alarm if it reads the notification indicator sent in any other frame or if it reads multiple notification indicators. The wireless device can perform an AND of all the notification indicators detected by each desired service and can process the MCCH only if all detected notification indicators are established. However, to avoid losing signaling information due to detection errors, the wireless device can process the MCCH if any of the detected notification indicators is set or if some number or percentage of notification indicators are set. FIGURE 5 shows a process 500 performed by a base station to transmit the notification indicators for the broadcast and multicast services supported by the base station. The base station maps the services into random sequences, a random sequence for each service (block 512). This can be achieved by mapping the identifier (eg, the TMGI) for each service of an NI value, for example, as shown in equation (4). The base station then generates a random sequence for each service based on a unilateral function (for example, as shown in equation (2) or (5)) a PN generator (for example, as shown in equation (6)). )) and the identifier or value NI for the service (block 514). Regardless of how the random sequence is generated, each random sequence is associated with a specific location to send a notification indicator in each frame. The locations for the notification indicators in the different frames for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence. The base station determines a notification value (either 0 'or Y') for each service in each modification period (block 516). For each service, the base station establishes the notification indicators for all the frames in the modification period or for the notification value for the service of that modification period. The base station also determines the value of the indicator to send for each location in which multiple notification indicators for multiple services map the same location. In any case, the base station transmits the notification indicators for each service in the random locations determined by the random sequence for that service (block 518). The base station also transmits search indicators for each inactive wireless device in PICH in the frames allocated in the wireless device and in the locations determined by the PICH sequence for the wireless device. FIGURE 6 shows a process 600 performed by a wireless device to receive notification indicators for at least one service desired by the wireless device. The wireless device determines the random sequence for each service in a similar manner as the base station (block 612). The wireless device also determines the frames or search occasions in which to receive the search indicators (block 614). For each of these inactive frames, the wireless device receives the notification indicator for each service in the MICH at the location determined by the random sequence for the service (block 616). The wireless device also receives the search indicator by itself at the PICH at the location determined by the PICH sequence by the wireless device (block 618). The wireless device may choose to read any number of notification indicators for each service based for example on the desired false alarm probability. The wireless device can be activated more frequently than its DRX cycle to receive more notification indicators and thus lower the probability of false alarm. In any case, the wireless device determines a notification value for each service in each modification period based on all the notification indicators received by that service in that modification period (block 620). Randomization of indicator locations for random sequences is introduced in additional time dimension capacity. This randomization also ensures that the collisions between the notification indicators for the different services are spread uniformly across all services and do not correlate between any of these services. The probability that notification indicators for two different services overlap over a whole modification period is minimized. A wireless device is capable of reducing the probability of false alarm for a desired service given by reading the MICH multiple times during the modification period to detect multiple notification indicators for the service. The wireless device can then process the MCCH if all detected notification indicators are established. The detected reporting indicators are less likely to overlap the notification indicators for any of the other services supported by the system. The false alarm probability, which is the probability that all detected notification indicators are set to l 'by some other services, is relatively low and dependent on the load on the MICH. The probability of false alarm can be reduced by reading more notification indicators for the desired service. The wireless device can achieve a very low probability of false alarm by reading all the notification indicators for the desired service, for example, if a wireless device is actively receiving the service. The false alarm performance for the three randomization schemes described in the above was analyzed. The analysis assumes that each notification indicator can be detected without error by the physical layer and any error is due to the overlap between the notification indicators for different services. For simplicity, the analysis also assumes that the indicator locations used for each service are perfectly random and the probability of an overlap between the two reporting indicators in different frames is perfectly independent. The system notification load is denoted as Pioad and represents the probability that a given notification indicator is set to? L 'in the MICH. The number of notification indicators that is detected for each desired service in each modification period is denoted as Nni. For each service, the notification indicators are set to the same notification value for the entire modification period. All notification indicators detected Nn? for a given service given can they be equal to? l 'if a notification value of? 1 'is sent to indicate a notification for the desired service. If any of the detected notification indicators Nn? -1 is equal to v0 'then a notification value of' 0 'can be presumed to have been sent for the desired service., and any detected notification indicators that are equal to xl 'are presumed to have been established by the collision with the notification indicators for other services. To explain possible detection errors by the physical layer, a detection algorithm can declare a notification value of 0 'if at least two detected notification indicators are equal to' 0 'and can declare a different notification value of l' . For this detection algorithm, a false alarm can occur if at least Nn? -1 detected notification indicators falsely indicate the presence of a notification. For the detection algorithm described above, the probability of false alarm for a given service pserice can be expressed as: where denotes the number of different combinations of K reporting indicators between Nni reporting indicators. If a wireless device is interested in multiple services (Nser) then the probability of false alarm for the wireless device, P ^ 106, can be expressed as: A computer simulation was performed to determine the false alarm probability for a given wireless device with the three randomization schemes described above. The following parameter values were used for the simulation: Nn = 144, G = 216, Nni = 5, and N? Er = 10. Table 1 shows the probability of false alarm for the wireless devices for each randomization scheme and for different notification loads for the system. The simulation results indicate that the three randomization schemes provide lower probability of false alarm than without randomization, for example, using equation (1). The results of the simulation also indicate that the false alarm probability is lower with the unilateral function shown in equation (2) and the PN generator shown in equation (6).

Table 1- Probability of false alarm (QPSK) for the search indicators. Each search indicator is represented by a modulation symbol set. With QPSK, each modulation symbol is transmitted at a predetermined power level. The same transmit power point is used for each modulation symbol regardless of whether a value of? 0 'or? L' is sent for the search indicator. The MICH can be designed to use on / off modulation (OOK) for notification indicators, which can reduce the amount of transmission power for the MICH. With OOK, a notification indicator value? 1 'is transmitted at a predetermined power level, and a notification indicator value 0' is transmitted with zero power (i.e., not transmitted). The transmit power for a notification indicator sent with OOK must be twice the transmit power for a notification indicator sent with QPSK to achieve the same detection performance for OOK and QPSK. The transmission power for the MICH is determined by the MICH load, which is the average fraction of the notification indicators that are sent to * 1 'in a given frame. A reduction in the total transmission power for the MICH is achieved if the MICH load is less than 50%. The MICH load is likely to be less than 50% in order to avoid high false alarm ratios for wireless devices. In this way, the use of OOK will likely reduce the total transmission power for the MICH for the same QPSK detection performance. FIGURE 7 shows a block diagram of a mode of a base HOx station and a wireless 120x device. In the base HOx station, an encoder 710 receives traffic data for search and other messages, processes (eg, encodes, tags, and maps by symbol) the traffic data and generates modulation symbols. A modulator 712 performs channeling, spectral propagation, scrambling, etc., on the modulation symbols for several physical channels (e.g., PICH, MICH, and S-CCPCH) and provides a stream of data chips. A transmitter unit 714 (TMTR) conditions (e.g., analogizes, amplifies, filters and up-converts by frequency) the data chips and generates a downlink signal, which is transmitted by an antenna 716. The wireless 120x device , an antenna 752 receives the downlink signal from the base station HOx and provides a received signal to a receiver unit 754 (RCVR). Receiving unit 754 conditions (eg, filters, amplifies, and down-converts by frequency) the received signal, digitizes the conditioned signal, and provides data samples. A demodulator 756 (Demod) processes the data samples and provides symbol estimates. The demodulator 756 further performs detection for notification indicators and search indicators as directed by a controller 760. A decoder 758 processes (e.g., desmaps, deinterleaves, and decodes) the symbol estimates and provides decoded data for messages sent by the base HOx station. The controllers 720 and 760 direct the operation at the base HOx station and the wireless 120x wireless device, respectively. The controller 720 and 760 can also perform various functions for transmitting and receiving, respectively, notification indicators and search indicators. For example, the controller 720 can perform the process 500 in FIGURE for the transmission of notification indicators, and the 760 controller can perform the 600 process in the FIGURE 6 for the reception of notification indicators. Memory units 722 and 762 store data and program codes for controllers 720 and 760, respectively. A timer 764 provides the timing information, which is used for the controller 760 to determine when to activate to process the PICH and the MICH. The notification transmission and reception techniques described herein can be implemented by various means. For example, these techniques can be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units used to transmit the notification indicators may be implemented within one or more specific application integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD). , programmable logic devices (PLD), programmable field gate devices (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 notification indicators may also be implemented within one or more ASICs, DSPs, etc. For a software implementation, the techniques of transmitting and receiving notification can be implemented with modules (eg, procedures, functions, etc.) that perform the functions described herein. The software codes may be stored in a memory unit (e.g., memory unit 722 or 762 in FIGURE 7) and executed by a processor (e.g., controller 720 or 760). The memory unit may be implemented within the processor or be an external part of the processor, in which case it may be communicatively coupled to the processor by various means as is known in the art. The prior description of the described embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but to be in accordance with the broadest scope consistent with the principles and novel features described herein.

Claims (41)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property.
2. CLAIMS 1. A method for transmitting notifications in a communication system, characterized in that it comprises: mapping a plurality of services in a plurality of random sequences, a random sequence for each service, each random sequence is associated with a location for sending a flag of notification in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence; and transmit notification indicators for service in the locations determined by the random sequence for the service. The method according to claim 1, further characterized in that it comprises: generating the plurality of random sequences based on a unilateral function and the identifiers for the plurality of services.
3. 3. The method according to claim 1, further characterized in that it comprises: generating the plurality of random sequences based on a unilateral function comprised of a first function of the frame number randomized by a second function of the service identifier.
4. The method according to claim 1, further characterized in that it comprises: generating the plurality of random sequences based on a pseudo-random number generator (PN) and identifiers for the plurality of service.
5. 5. The method according to claim 1, further characterized in that it comprises: determining a notification value for each service; and establishing a plurality of notification indicators for each service in the notification value for the service.
6. The method according to claim 5, characterized in that the transmission of the notification indicators for each service comprises transmitting the plurality of notification indicators for each service in a plurality of consecutive frames and the locations determined by the random sequence for the service.
7. 7. An apparatus in a communication system characterized in that it comprises: an operating controller for mapping a plurality of services in a plurality of random sequences, a random sequence for each service, each random sequence being associated with a location for sending a notification indicator in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence; and an operating processor for mapping the notification indicators for each service for the locations determined by the random sequence for the service.
8. The apparatus according to claim 7, characterized in that the controller is also operative to generate the plurality of random sequences based on a unilateral function for a pseudo-random number generator (PN) and also based on identifiers for the plurality of services .
9. The apparatus according to claim 7, characterized in that the controller is further operative to determine a notification value for each service and to establish a plurality of notification indicators for each service for the notification value for the service.
10. The apparatus according to claim 9, characterized in that it comprises: a transmitter operative to transmit the plurality of notification indicators for each service in a plurality of consecutive frames and in the locations determined by the random sequence for the service.
11. 11. The apparatus according to claim 7, characterized in that the plurality of services are broadcast and multicast services.
12. 12. An apparatus in a communication system, characterized in that it comprises: means for mapping a plurality of services in a plurality of random sequences, a random sequence for each service, each random sequence is associated with a location for sending a notification indicator in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence; and means for transmitting notification indicators for each service in the locations determined by the random sequence for the service.
13. The apparatus according to claim 12, further characterized in that it comprises: means for generating the plurality of random sequences based on a unilateral function or a pseudo-random number generator (PN) and also based on identifiers for the plurality of services.
14. The apparatus according to claim 12, further characterized in that it comprises: means for determining a notification value for each service; means for establishing a plurality of notification indicators for each service in the notification value for the service; and means for transmitting the plurality of notification indicators for each service in a plurality of consecutive frames and in the locations determined by the random sequence for the service.
15. 15. A method for transmitting notifications in a communication system, characterized in that it comprises: determining a location to send a notification indicator for a service based on a frame in which the notification indicator is sent and an identifier for the service, the identifier is used to randomize the location for the notification indicator within the frame; and transmit the notification indicator 'for the service at the location in the frame.
16. 16. The method according to claim 15, characterized in that the determination of the location to send the notification indicator is based on the following equation:

    q =. { [C x (NI T ((C SFN) modG))] modG} x-Nn G

    where C and G are two constants; SFN is a system frame number for the frame; ? n is the number of available locations in the frame; ? I is a value determined by the identifier for the service; ? denotes an exclusive OR operation (XOR) of type bit; mod denotes a module operation; LxJ is a floor operator that provides the next lower integer value for x; and q is the location for the notification indicator within the frame.
17. 17. The method according to claim 15, characterized in that the transmission of the notification indicator comprises: transmitting the notification indicator for the services at the location in the frame and using the On / Off modulation.
18. The method according to claim 15, further characterized in that it comprises: establishing a plurality of notification indicators for the service at a notification value selected for the service; determining random locations in a plurality of frames based on the identifier for the service; and transmitting the plurality of notification indicators for the service at the random locations in the plurality of frames.
19. 19. An apparatus in a communication system, characterized in that it comprises: means for determining a location for sending a notification indicator for a service based on a frame in which the notification indicator is sent and an identifier for the service, the identifier it is used to randomize the location for the notification indicator within the frame; and means for transmitting the notification indicator for the service at the location in the frame.
20. 20. The apparatus according to claim 19, characterized in that the means for determining the location to send the indicator of

    Notification is based on the following equation:

    Nn 4 =. { [C x (NI? ((CxSFN) mod G))] modG} x- G

    where C and G are two constants; SFN is a system frame number for the frame;

    Nn is the number of locations available in the plot;

    NI is a value determined by the identifier for the service; ? denotes an exclusive OR operation (XOR) of type bit; mod denotes a module operation; LxJ is a floor operator that provides the

    next lower integer value for x; and q is the location for the notification indicator within the frame.
21. 21. A method to receive notifications for at least one service in a communication system,

    characterized because it comprises:

    determine at least one random sequence

    for at least one service, a random sequence for each service, each random sequence is associated with a location to send a notification indicator in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for notification indicators for each remaining random sequence; and receiving notification indicators for each of at least one service in the locations determined by the random sequence for the service.
22. 22. The method according to claim 21, further characterized in that it comprises: determining frames in which to receive search indicators; and receive the notification indicators for at least one service and the search indicators in the determined frames.
23. 23. The method according to claim 21, further characterized by comprising: obtaining at least two notification indicators in each modification period for each of at least one service, the notification indicators for each service are established in the same notification value in each modification period; and determining a notification value for each service in each modification period based on at least two notification indicators obtained in the modification period for the service.
24. 24. The method according to claim 21, further characterized by comprising: determining the number of notification indicators to receive in each modification period for each service based on a desired false alarm probability.
25. 25. The method according to claim 21, further characterized in that it comprises: generating at least one random sequence based on a unilateral function and an identifier for each service.
26. 26. The method according to claim 21, further characterized in that it comprises: generating at least one random sequence based on a unilateral function comprised of a first function of a frame number randomized by a second function of the service identifier.
27. 27. The method according to claim 21, further characterized in that it comprises: generating at least one random sequence based on a pseudo-random number (PN) generator and an identifier for each service. The method according to claim 21, further characterized by comprising: determining the location for the notification indicator for each service in each frame based on the following equation:

    q = Nn. { [Cx (NI T ((CxSFN) modG))] modG} x G

    where C and G are two constants; SFN is a system frame number for the frame; Nn is the number of locations available in the plot; NI is a value determined by the identifier for the service; ? denotes an exclusive OR operation (XOR) of type bit; mod denotes a module operation; LxJ is a floor operator that provides the next lower integer value for x; and q is the location for the notification indicator within the frame. 29. An apparatus in a communication system, characterized in that it comprises: an operating controller for determining at least one random sequence for at least one service, a random sequence for that service, each random sequence is associated with a location for sending a notification indicator in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for the notification indicators for each remaining random sequence; and an operational demodulator to detect the notification indicators for each of at least one service at the locations determined by the random sequence for the service. 30. The apparatus according to claim 29, characterized in that the controller is also operative to determine the frames in which to receive the search indicators, and where the demodulator is also operative to detect the notification indicators for at least one service and the search indicators in the determined frames. The apparatus according to claim 29, characterized in that the demodulator is operative to detect at least two notification indicators in each modification period for each of at least one service and to determine a notification value for each service in each notification period based on at least two notification indicators obtained in the modification period for the service. 32. The apparatus according to claim 29, characterized in that the controller is also operative to generate at least one random sequence based on a unilateral function or a pseudo-random number (PN) generator and also based on an identifier for each service. 33. An apparatus in a communication system, characterized in that it comprises: means for determining at least one random sequence for at least one service, a random sequence for each service, each random sequence is associated with a location for sending an indicator of notification in each frame, where the locations for the notification indicators for each random sequence are randomized with respect to the locations for notification indicators for each remaining random sequence; and means for receiving notification indicators for each of at least one service at the locations determined by the random sequence for the service. 34. The apparatus according to claim 33, further characterized in that it comprises: means for determining frames in which to receive search indicators; and means for receiving the notification indicators for at least one service and the search indicators in the determined frames. 35. The apparatus according to claim 33, further characterized in that it comprises: means for obtaining at least two notification indicators in each modification period for each of at least one service, the notification indicators for each service are established at the same notification value in each modification period; and means for determining a notification value for each service in each modification period based on at least two notification indicators obtained in the modification period for the service. 36. The apparatus according to claim 33, further characterized in that it comprises: means for generating at least one random sequence based on a one-sided function or a pseudo-random number generator (PN) and in addition is based on an identifier for each service. 37. A method for transmitting notifications in a communication system, characterized in that it comprises: determining a plurality of notification indicators for a plurality of services;

    mapping the plurality of notification indicators for a plurality of locations in a frame; and transmitting the plurality of notification indicators using On / Off modulation. 38. The method according to claim 37, characterized in that the transmission of the plurality of notification indicators comprises: transmit notification indicators of a first value at a predetermined power level, and transmit notification indicators of a second value with power null 39. The method according to claim 38, further characterized in that it comprises: limiting an expected number of notification indicators with the first value in the frame to less than fifty percent. 40. An apparatus in a communication system, characterized in that it comprises: means for determining a plurality of notification indicators for a plurality of services; means for mapping the plurality of notification indicators in a plurality of locations in a frame; and means for transmitting the plurality of notification indicators using On / Off modulations. 41. The apparatus according to claim 40, characterized in that the means for transmitting the plurality of notification indicators comprises means for transmitting notification indicators of a first value at a predetermined power level, and means for transmitting notification indicators of a second value with zero power.