MXPA00011005A - Random access in a mobile telecommunications system - Google Patents

Abstract

An uplink common physical channel (random access channel) frame structure is disclosed with a separate preamble and data portion. The preamble is used by a base station to detect that a mobile station is attempting a random access request. The data portion of the channel includes user data, and pilot symbols that provide energy for channel estimation during reception of the data portion. A guard interval (TG) is preferably inserted between the preamble and data portion of the frame, which enables data detection to occur during an idle period. As such, the frame structures for both the common physical (random access) uplink channel and dedicated physical (traffic) uplink channel are compatible.

Description

RANDOM ACCESS IN A MOBILE TELECOMMUNICATION SYSTEM BACKGROUND OF THE INVENTION Technical Field The present invention relates, in general, to the field of mobile telecommunications, in particular, to a method and system for processing multiple random access calls in a Multiple Access Division.

Code (CDMA) or a CDMA Broadband System (WCDMA). Description of the Related Art For next-generation mobile communication systems, such as IMT 000 and the Universal Mobile Telecommunications System (UMTS), Direct Sequence CDMA (DS-CDMA) approaches have been proposed for use in United States, Europe and Japan. In this regard, a similar CDMA system is being considered for use in both Europe and Japan, but a somewhat different CDMA concept is being considered for use in the United States. Next-generation systems will require that they provide a broad selection of telecommunications services including digital voice, video and packet data, and channel switched circuit modes. As a result, it is expected that the number of calls will increase significantly, which will result in a much higher traffic density in random access channels (RACHs). Unfortunately, this increased traffic density will also result in increased collisions and access failures. Consequently, the new generation of mobile communication systems will have to use faster and more flexible random access procedures in order to increase their successful access rates and reduce access request processing times. In other words, there will be a great demand for much faster and more efficient access to those systems due to the expected substantial increase in packet switched traffic. The proposed WCDMA approach includes two different ways of transmitting packets, on a common channel and on a dedicated channel. However, there will be high demand for faster and more efficient random access using any of the transmission schemes. For example, in patent applications of the United States 08 / 733,501 and 08 / 847,655 and in provisional patent application 60 / 063,024 said random access approach is described, which can be used for a package-based service in where a mobile station (MS) can transmit packets on a common channel and on a dedicated channel. In the case of the common channel, the packages are included in the random access requests that are being transmitted. In the case of the dedicated channel, the random access requests that are being transmitted include requests for a dedicated channel in which to transmit the associated packets. The patent applications described above reveal a random access approach? Lotted-ALOHA (segmented ALOHA) (S-ALOHA). Using this approach, a common transmission medium can be shared by a plurality of users. Essentially, the transmission means is divided into a plurality of access segments, which are characterized by a time deviation relative to the limit of the reception frame. Each user (MS) randomly selects an access segment and then transmits its information message in that access segment. However, a disadvantage of this approach is that access segments are not assigned to users, which can result in collisions between transmissions from different users. For example, using the random access approach S-ALOHA of the above-described patent applications, an MS generates and transmits a random access request. A diagram illustrating a structure for said random access is shown in Figure 1. The structure shown is used in the first two patent applications described above. As shown, the random access request comprises a preamble and a data field portion. The preamble part is used mainly as a call function. The data portion includes the request and / or the data packet. In order to reduce the risk of collisions of requests from different MSs that select the same access segment, the preamble for each MS request contains a unique signature pattern (bit o). The MSs randomly select the signature pattern used (preferably from a limited set of signature patterns), which further reduces the risk of collisions. The following procedure is typically used in an S-ALOHA random access system. First, an MS is synchronized with a base station. The MS "listens" to a transmission channel over which, for example, the network transmits random access codes, transmission channel transmission power level and the level of interference signal measured in that base station. Next, the MS estimates the downlink loss, and together with the knowledge of the interference signal level of the base station and the transmission power level, estimates the level of transmission power to be used. The MS selects a segment of access and a signature pattern, and transmits your random access request in the selected access segment and with the selected signature pattern. The MS waits for a response to the access request from the base station. If the MS does not receive a response from the base station within a predetermined period (time termination), the MS selects a new access segment and a signature pattern, and transmits a random access request. With reference to FIGURE 1, the preamble portion is modulated with different signature patterns, and scattered with a unique dispersion code of the base station. The signature patterns are used to separate different simultaneous random access requests, and also to determine which dispersion-mixed code to use in the data portion of the requests. Consequently, as mentioned above, requests from two different MES that use the same access segment but with different signature patterns can be separated. Also, the pilot symbols can be inserted within the data portion of the request, in order to fatate coherent detection. The preamble portion of the request can also be used for coherent detection, but if the data portion is relatively long, the estimate The channel has to be updated accordingly. FIGURE 2 illustrates the structure of the random access request described in the third of the patent applications described above. Using the structure shown, the data portion is transmitted in the I branch of the channel, and the pilot preamble is transmitted in the Q branch. The structure is used in order to make the access channel compatible with the other channels of communication. dedicated uplink, which for the WCDMA approach are multiplexed I / Q. In any case, it does not matter if the data or pilot symbols are multiplexed in time, multiplexed I / Q or multiplexed with code (which can be carried out among other methods by complex mixing of an I / Q multiplexed signal). A frame is divided into a number of time slots in the dedicated channel according to the power control command speed. These segments are indicated box segments. In the proposed WCDMA systems, there are 16 of these segments from frame to frame. In a random access scheme, a table is also subdivided into a number of access segments, but the purpose is to increase the efficiency of the random access process. An access segment defines a period in which an M? Due to start your transmission of a random access request. Using the random access approach in the first two of the patent applications described above, random access requests can, for example, be transmitted in consecutive access segments as shown in FIGURE 3. The data portion of the requests random access shown in FIGURE 3 are mixed by a long code (the same length as the data portion). Consequently, an access segment plus a guard time may be equal to the N-frame segments. Preferably, the preambles of different access segments should not overlap, because many preamble detectors will be required in the base station, and the interference (due to the same dispersion codes used) will be increased for the random access detection process. However, for the frame structure used in the third of the patent applications described above, the efficiency of the random access channel may be reduced, because the longer preambles are used and the preambles of different access requests should not overlap. . The random access receiver in the base station comprises two sections, wherein a section detects the preamble, and the second section detects the data portion of the request. The section that detects the preamble includes an attached filter, which is coupled to the dispersion code used in the signatures. The modulation of the output signal of the coupled filter is eliminated by multiplication with the expected signature symbols (remodulation), in order to separate the random access requests of different MS having different signatures. When registering a random access request in the preamble detector section of the base station receiver, a plurality of RAKE fingers are assigned in order to detect the data portion of that request. Also, the section of the preamble detector couples the frame time of the data portion of the request with the RAKE receiver, together with the spreading code used in the data portion, and an initial estimate of the channel response. The RAKE receiver detects data from the data portion, and the base station processes the data and responds to that random access request from that base station. One problem with the approach of the above-mentioned patent application is that the random access channel used is not compatible with other uplink channels used in the proposed WCDMA approach.

Consequently, the new equipment needs to be developed for the data portion of the random access channel. A problem with the approach of the third patent application described above is that although it avoids the compatibility problem of the uplink channel, it requires a significant amount of additional damping. Another problem with this approach is that the processing speed of random access request messages is reduced, because the preambles of different access segments should not overlap, and the preambles in this approach are relatively long. One problem with the third random access approach (described in the third patent application), which does not exist for other approaches, is that if the data portion is longer than the access segment, then there may be ambiguity in the Time detection of the frame. In that case, the pilot symbol of each access segment can carry a signature which is the same in each access segment, or the signature can be changed from access segment to access segment. As such, there may be a plurality of times during transmission when a signature is detected. However, the base station receives a time signal per segment of access, and therefore, there may be a problem in determining the exact frame time. Although this problem can be solved by existing means, such a solution is quite complicated. An additional problem with this approach is that during the random access detection process, the entire access segment has to be buffered for the detection of subsequent data until the random access request has been detected by decoding the transmitted signature pattern simultaneously, this step uses an access segment to complete and therefore requires a maximum cushioning of a full access segment. Additional damping is also required during the detection of the portion of data used in the two other approaches (as well as in the method of the present invention), because the channel estimate has to be carried out based on a channel pilot transmitted continuously (focus three above), or pilot symbols periodically inserted (focus one above). In other words, the channel estimates have to be provided in parallel with each received data symbol. The required damping is only for the duration required to calculate the related channel estimate (being this, transmitted during the same time) with a data symbol. An illustrative example of the process of multiple random access calls in mobile communication is given in WO 9818280 A2 which generally describes a mobile communication system in which random access packets are transmitted which include a preamble field and other data fields used to facilitate the establishment of calls and allocation of resources. The preamble may contain a signature pattern and be dispersed by a scatter code. Another illustrative example of the processing of multiple random access calls in mobile communication is given in Proceedmgs of the IEEE International Conference on Universal Personal Communication, ICUPC '97, October 1997, pages 3 to 47. which describes a random access method with segmented ALOHA base for CDMA systems, including an access box structure that has preamble and data fields. The random access table is scattered with a scatter code. COMPENDIUM OF THE INVENTION According to a preferred embodiment of the present invention, a frame structure of a common physical uplink channel (access channel) is provided random) with a separate preamble and data portion. The preamble is used by the base station to detect that an MS is attempting the random access request. The data portion of the channel includes user data and pilot symbols that provide power for channel estimation during reception of the data portion. A guard interval is inserted preferably in the preamble portion in the box, which enables the detection of data that occurs before the current data detection process starts. Consequently, the damping of data can be minimized. An important technical advantage of the present invention is that the frame structure in the common physical uplink channel is compatible with the frame structure in the dedicated physical uplink channel. Another important technical advantage of the present invention is that each portion of the random access request has to satisfy only one function and therefore be optimally designed for that respective work. Yet another important technical advantage of the present invention is that the same allocation code scheme can be used for both the data portion of the random access request and the channels dedicated uplink Yet another important technical advantage of the present invention is that all subsequent necessary processing, such as, for example, signature decoding, can be carried out during the guard period. Consequently, the design of the equipment for the detection of random access request can be simplified, and the processing of the random access request can be minimized. Yet another important technical advantage of the present invention is that the same equipment of the receiver can be used to decode both the data portion of the common physical uplink channel and the dedicated physical uplink channel, which unifies the design of the equipment and decreases the cost of the equipment. Yet another important technical advantage of the present invention is that RAKE volume receivers or RAKE aedos can be allocated or shared by both the common physical channel (random access data packet) and the dedicated physical channel (traffic channel), which can be assigned or shared. which minimizes the amount of equipment required. Yet another important technical advantage of the present invention is that the buffer size requirements can be minimized, because the functions of the preamble portions and data of the random access request are separated. Yet another important technical advantage of the present invention is that the speed of random access requests can be increased compared to other random access approaches. In particular, the speed of random access requests for the third random access approach described above would be less than for the present invention for the same amount of equipment used. Yet another important technical advantage of the present invention is that the ability to transmit random access messages at different speeds can be obtained in a very flexible manner. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the method and apparatus of the present invention can be obtained with reference to the following detailed description when taken in conjunction with the accompanying drawings in which: FIGURE 1 is a diagram illustrating a frame structure of existing channel for a random access request; FIGURE 2 is a diagram illustrating an existing channel frame structure for a random access request; FIGURE 3 is a diagram illustrating an existing channel frame structure for random access requests made in consecutive (time) segments; FIGURE 4 is a diagram illustrating an I / Q multiplexed frame structure for random access channel in a WCDMA mobile communication system, according to a preferred embodiment of the present invention; FIGURE 5 is a code tree diagram illustrating an example of the code allocation pipeline for the data portion of a random access request to be transmitted by an MS, in accordance with a preferred embodiment of the present invention; FIGURE 6 is a simplified block diagram of an exemplary system for use in assigning a RAKE receiver component to disperse the data portion of a random access request detected in a WCDMA base station receiver, in accordance with a modality preferred of the present invention; FIGURE 7 is a diagram showing relevant details of an exemplary random access detector unit that can be used to implement the functions of the random access detector unit shown in FIGURE 6; FIGURE 8 is a block diagram showing pertinent details of an example searching unit that can be used to implement the functions of the searching unit shown in FIGURE 6; and FIGURE 9 is a block diagram showing pertinent details of an exemplary RAKE finger that can be used to implement the functions of a RAKE finger shown in FIGURE 6. DETAILED DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention and its advantages are better understood with reference to FIGURES 1 to 9 of the drawings, wherein similar numbers are used for equal and corresponding parts of the plurality of drawings. Essentially, in accordance with the preferred embodiment of the present invention, a common physical channel frame structure (random access channel) is provided with a separate data portion and preamble. The preamble is used by the base station to detect that an MS is attempting a random access request. The data portion of the channel includes user data, speed information and pilot symbols that provide power for channel estimation during the detection of the data portion. A guard interval is inserted preferably between the preamble and the data portion of the box, which allows the preamble to be detected before the data arrives (requiring less dampening). As such, the frame structures for both the common physical uplink channel (random access) and the dedicated physical uplink channel (traffic) are compatible. Specifically, FIGURE 4 is a diagram illustrating the frame structure for a random access channel in a WCDMA mobile communication system, in accordance with a preferred embodiment of the present invention. The lower set of arrows represents the tempopzación of an existing frame structure, which is provided in it for the purpose of comparison. The preamble portion of the frame structure shown in FIGURE 4 can be optimally designed for random access detection and signature detection. As such, a base station can continuously "listen" for said transmitted preamble. In order to distinguish between simultaneous random access requests that are transmitted by different MSs, each random access request preamble is modulated by means of a unique signature pattern, which is randomly selected by the respective MS transmitting the request. An example of said signature preamble modulated in a request for Random access is described in the first two patent applications described above, which are fully incorporated into the present invention in its entirety. As such, the signature pattern for each preamble is randomly selected by the MS from a plurality of orthogonal codes. For this mode, each of the orthogonal codes has a length of 2Nslg symbols, and is scattered with a unique base station dispersion code (this being the dispersion code number provided above by means of the channel transmission channel) . The Nslg parameter is the order number of the detected signature pattern. Each of said symbols is scattered by the same sequence of code of length SF, where SF indicates the dispersion factor of the code. Typically, the resulting length of the preamble (example: SF * 2Nslg / Rc__P, where h? P is the chip rate or the dispersion sequence rate) is less than the length, N * Tts »of N time segments in existing systems. Accordingly, according to the present invention, a guard time interval, TG, can be generated by interrupting the transmission power of the MS from the end of the preamble to the start of the next time segment. The time (or length) of the table new is represented in FIGURE 4 as TPA (preamble time or length) plus TG (length of the guard time interval) plus TD (time or length of the data portion of the frame). This novel random access frame structure and method can reduce the transmitted power of the MS (example, albeit slightly, by interrupting the transmission during the interval between the preamble and the data portion of the random access request), and the time The random access request can be aligned exactly at the time of the frame segment scheme of existing systems. Additionally, according to the preferred embodiment, during the period of the protection period interval. TG, the signature detection process can be carried out at the base station receiver (example, using the Walsh-Hadamard fast transformation), and the base station can determine more quickly if the random access request has been made. Subsequently, as described in detail below, an available RAKE receiver or RAKE finger (example, depending on how many delay tracks are to be used) can be assigned, and during the protection time interval, TG, the initial values of the process signature detection can be brought to the selected RAKE unit, which is earlier in time to existing systems. An example of the use of said protection time slot for random access request detection is where a preamble of 16 long symbols and a spread with an Orthogonal Gold code of 256 chips long. In a system that operates at 4,096 Mchips / sec, the preamble will be 1 ms long. In the proposed WCDMA systems, there will be 16 frame segments for every 10 ms. Theoretically, a protection time interval, TG, in this example can be 0.25 ms long. Also in accordance with the preferred embodiment of the present invention, the data transmission portion of the novel uplink common physical channel shown in FIGURE 4 can be designated independently of the preamble requirements of the random access. For example, in order to achieve a unified equipment design, it is preferable to use the same data and control structures (example, pilot and pilot information and speed) both in the common physical channel and in the dedicated physical channel (this being the channel typically used for data traffic). As such, according to the novel frame structure of the present invention, the pilot symbols may be dispersed according to the dispersion scheme of the uplink physical channel, and therefore do not require any signature modulation. Consequently, (for example, compared to the third patent application mentioned above), the present invention offers significantly greater freedom in the selection of the pilot field length and additional common data (for example, speed indicator or Rl field). Additionally, with respect to FIGURE 4, the pilot symbols that are being transmitted may be multiplexed I / Q code, or alternatively time multiplexed or code multiplexed with the data. FIGURE 5 is a code tree diagram illustrating an example of channelization code assignment for the data portion of the random access request to be transmitted by an MS, in accordance with the preferred embodiment of the present invention. In order to illustrate how dispersion and mixing can be carried out for the data portion of the random access request, the example shown illustrates how 16 different signature patterns can be used in the data portion. For the example shown, the signature pattern used for the preamble of the random access request points to one of the 16 nodes in the code tree that includes channelization codes of length 16. The sub-tree shown below the selected node may be used to disperse the data portion of the request. For example, with reference to FIGURE 5, the MS disperses the control part (eg, the pilot of the Q branch) with a channelization code having a dispersion factor of 256 at the bottom of the sub-tree (example , for signature 16), then for the data part (eg, for branch I), the MS can use any of the channelization codes with a dispersion factor of 32 to 256 at the top of the sub-tree. Of course, there are other alternatives. Additionally, for the purpose of improved cross-correlation, the data portion of the transmitted request may also be mixed with a mixing code having the same length of the data portion (and, for example, may be a complex code). In accordance with the present invention, the size of the data portion of the random access request may be variable. The problem associated with the proposed WCDMA system requirement for different rates of random access requests in the random access channel is solved by means of the present frame structure which it allows the use of different dispersion factors of the data portion of the request (resulting in different amounts of data per request), and data fields that have different lengths in time (also resulting in different amounts of data per request). For example, the use of different speeds for random access requests in a random access channel can be illustrated as follows. The different sets of signatures used can point to different dispersion factors and / or lengths of the data portions. By having the base station transmit a predetermined number of signatures to be assigned at a certain data rate, the base station can adapt the combination of signatures and data rate to the current conditions of the traffic request being made. As a further example, the MS may include an Rl field at the beginning of the data portion of the random access request. The control portion of the request has a known dispersion factor (for the base station) (and therefore also the code) and, therefore, can be easily detected in the base station. As such, the data portions of different random access requests that have both different lengths and different scattering factors can also be easily detected by the base station. Yet another example of the advantageous use of variable-sized data portions of random access requests in a WCDMA system, an Rl can be dispersed over the entire control portion of a request (eg, using a dispersion approach similar to that used in existing dedicated uplink channels). However, this approach may require the use of additional damping for the data portion of the requests. Alternatively, an Rl can be included at the beginning of the data field of the request, which can be used for different lengths (in time) of the data portions. Another example is a form of blind speed detection. In the detection of variable length data portions, a cyclic redundancy check (CRC) can be carried out in predetermined lengths. The coding only continues for the next possible length of time. At the base station, the detection of the different dispersion factors is carried out by initiating the detection of the smallest dispersion factor observed, and if the CRC result is valid, start the detection of the next longer dispersion factor, and thus successively.

As such, for each of the variations above, it is preferable to have a relatively small set of different speeds to select from, in order to minimize signaling overload and / or receiver complexity. Also, it is preferable to have the length of the data field divisible by the length of the time segment of other uplink channels in the system. FIGURE 6 is a simplified block diagram of an exemplary system (100) for use in assigning a RAKE receiver component to disperse a portion of data from a detected random access request in a WCDMA base station receiver, according to the preferred embodiment of the present invention. Essentially, the random access detection function can detect signature patterns, estimate delays and also provide channel estimates, if desired. The example system 100 shown includes a random access detection unit 102 and at least one search unit 104. The structure of the receiver shown in FIGURE 6, without the random access detection unit 102, can be a receiver for a regular traffic channel. A function of the random access detection unit 102 is to detect-find as many access requests random as possible. This detection process (and a search process) provides, for example, track delay information. The detection of the data portion of the random access request is carried out in the RAKE receiver unit 108 using the track delay information of the random access detection unit 102. One or more search units 104 are coupled in parallel with the random access detection unit 102. As such, the random access detection unit 102 can be seen to function as a type of specialized search engine. The primary function of one or more of the search units 104 is to detect all propagation delays of the traffic channels that are being used. However, both the random access detection unit 102 and the one or more search units 104 provide track delay information, which is used in the RAKE receiver unit 108. The outputs of the random access detection unit 102 and one or more of the detection units 104 are coupled to the control unit 106. The control unit 106 uses the runway delay information, channel estimates and signature information in order to allocate the data portion information detected to a component 108a-108n of a unit RAKE receiver suitable for dispersion. The output of the control unit 106 couples a control signal of the RAKE receiver unit 108, which includes an order number of the detected signature pattern, N_lg, which is used to assign a data rate to the portion of Subsequent data to be entered into the RAKE receiving unit. The control signal of the control unit 106 also includes the track delay estimate, tv, which is used to set the delay correct in the RAKE receiver unit 108 to integrate the data portion into the input of the RAKE receiver unit. A channel estimation parameter, h, is coupled from the control unit 106 and used as the initial channel estimate in the RAKE receiving unit. 108. In accordance with the present invention, the use of the protection interval, Tr, between the random access request preamble and the data portion in the system 100 to carry out the entire post-processing described above during this inactive period. Consequently, the equipment requirements imposed to buffer the received input data can be minimized. Additionally, the use of a virtually identical structure for the portion of data of the request received for both channels Common and dedicated physics simplifies the design of the base station receiver. The advantages of this novel random access scheme are described above with respect to FIGURE 5. As mentioned above, the random access detection unit 102 can function as a specialized searcher. Both one or more search engines 104 and the random access detector unit 102 provide track delay information for use in the RAKE receiver 108. Accordingly, in accordance with the present invention, if all the uplink channels use a virtually identical scheme for the data portion of the random access request, each RAKE receiver component (or RAKE finger) 108a-108n may be assigned by the control unit 106 to integrate the received information into one of the propagation tracks. Consequently, a set of RAKE components can be shared for both dedicated physical channels (conventional uplink data), and for data packet transmissions in the common physical channel in the random access mode of the operation. Therefore, according to the random access scheme implemented by the present invention, the required number of RAKE components can be minimized.

FIGURE 7 is a block diagram showing pertinent details of an exemplary random access detector unit (202) that can be used to implement the functions of the random access detector unit 102 shown in FIGURE 6. Advantageously, a Baseband signal processing scheme (BB), which includes a complex inverse conversion on the front of the radio frequency (RF). The complex inverse conversion is carried out by mixing the received signal with a sine and cosine carrier (both carriers at the same frequency). The example random access detector unit 202 can be used for the I branch (for an antenna) of the random access receiver of the base station. A random access detector unit can be used for the Q branch. As such, the flow of the complex signals is signaled by the double line arrows. The random access unit 202 includes a filter 204. The filter, which is used only during the preamble period, is tuned to the spread code of the preamble (which has been provided to the MS by the base station). The filter 204 is used to detect the presence of the random access request, integrate the preamble part of the random access packet and couple the resulting signal to the accumulator. The accumulator it is comprised of a plurality of accumulator sections, each of which includes a block integral and discard module 206? -n (where i = 1 to n), and an associated signature generating section 208? -n. Each received preamble includes a unique signature pattern and each accumulator section (í-n) is tuned to one of the possible signature patterns to be received. Consequently, the different received random access requests can be separated by remodulating (205? -n) the output of the code filter 204 with the desired signature symbols (from the signature generating section 208? -n), and coherently accumulating the signals remodulated in the integrated block and discard modules 206? -n. The output of each accumulator section (integrated block and discard module 206? -n) is coupled to a respective peak detection unit 210? -n. At the end of the preamble period, each peak detection unit 210? -n searches for the output signal of its respective accumulator (module 206? -n) for each signal peak exceeding a predetermined detection threshold. Each peak detection unit 210? -n measures the position in time, TI-TK (this being, over the symbol periods of the preamble "M"), of the respective peak signal. If the absolute value of that signal exceeds a threshold default, the position of the related time value (time delay), t _-_? is taken to the control unit 106 and to the channel estimation unit 212 ?. The channel estimator can be used to provide initial values for a bandpass filter in the RAKE finger channel estimator 108a-n, which is assigned to demodulate the subsequent data portion of the random access request. These initial values, t ^ -hn, are taken from the integrated block and the discard modules 206 in the measured time positions, -_-._. As such, the accumulation result (complex peak value) in each time-lag position is output to the controller unit 106, to be used to select a RAKE finger 108a-n. The output of each channel estimation unit (accumulator branch) 212? -n corresponds to a respective signature pattern, S-Sn. FIGURE 8 is a block diagram showing details pertinent to an example lookup unit (304) that can be used to implement the functions of the search units 104 shown in FIGURE 6. The example search unit 304 includes a code filter 306, which is coupled to the pilot sequence of the dedicated data channel that is being used. The absolute value squared (308) of the output of complex signal of the filter 306 is (symbol by symbol) accumulated not coherently in the integral of the discard unit 310 due to the frequency deviations of the complex input signal. The track selection unit 310 (power delay spectrum or DPS), comparing each peak with a predetermined threshold value. The peak delays, t_-tM associated with the highest peak signal values are output to the control unit 106, to be used to select a RAKE finger 108a-n. FIGURE 9 is a block diagram showing the pertinent details of an example RAKE finger (408a-n) that can be used to implement the functions of a RAKE finger 108a-n shown in FIGURE 6. The RAKE receiver unit 108 it comprises a plurality of RAKE fingers 108a-n (3j3 example: 408a-n). Each finger 408a-n is assigned to a respective delay track (t) Each traffic user channel requires a RAKE receiver unit 108 (408) .The different delay track, tl, are compensated for by the use of a buffer of controlled variable delay 410. The initial setting for t_ is provided from the random access detector unit 202 in FIGURE 7 by means of the control unit 106 (FIGURE 6) and the tracking control unit 412. The current values for t_ may be provided from the search unit 304 in FIGURE 8 by means of the control unit 106 (FIGURE 6) and the search control unit 412, or is estimated with the delay time estimation unit 415. For a later option, the delay estimation unit 414 can be implemented with a late-delay delay disciple (fixed gauge delay technique) using the inputs of the code generator 413 and the delay damper 410, to calculate a delay of not coherent time. The received signal (input) is integrated (413) by the conjugate complex (416) of the original dispersion code used, and coherently accumulated (18) symbol by symbol. Each symbol received is weighted by a complex conjugate channel estimator, h * (? _). The channel estimate is calculated in a similar way by the channel estimation unit 414, but based on the pilot channel input. The integration of coherently accumulated pilot codes from the channel rejection and estimation unit 420 is passed through the band pass filter 422. The actual parts (420) of the receiver of the RAKE 108 finger unit. As such, the number of fingers RAKE assigned (per control unit 106) depends on the number of valid delay tracks, which are selected by the search units (104). Although the preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying drawings and described in the above Detailed Description, it will be understood that the present invention is not limited to the disclosed embodiment, but may present various adjustments, substitutions and modifications without departing from the spirit of the present invention as set forth and defined in the following Claims.

Claims (26)

1. CLAIMS na frame structure for a random access channel in a mobile communication system, comprising: a preamble that includes at least one signature; and a data portion comprising a control part and a data part, said at least one signature indicating a plurality of codes for dispersing said control part and said data part, wherein said plurality of codes includes a first code for dispersing said control part, and at least a second code to disperse said data part.
2. The frame structure of claim 1, wherein said first code and said at least second code are orthogonal to each other.
3. A frame structure for a random access channel in a mobile communication system, comprising: a preamble that includes at least one signature; and a data portion comprising a control part and a data part, said at least one signature indicating a plurality of codes for dispersing said control part and said part of data; wherein said plurality of codes includes a second plurality of codes for dispersing said data part, each of said second plurality of codes is associated with a plurality of scattering factors or with a respective scattering factor.
4. The frame structure of claim 1, wherein the first code and said at least one second code each is associated with a sub-tree of a code tree.
5. The frame structure of claim 3, wherein each of said second plurality of codes is associated with the same branch of a sub-tree of a code tree.
6. A frame structure for a random access channel in a mobile communication system, comprising: a preamble; a portion of data; and a protection portion between said preamble and said portion of data.
7. The frame structure of claim 6, wherein said preamble is modulated by a preselected signature pattern.
8. The frame structure of claim 6, wherein said preamble is modulated by a randomly selected signature pattern of a plurality of orthogonal codes.
9. The frame structure of claim 6, wherein the mobile communication system comprises a CDMA system.
10. The frame structure of claim 6, wherein said data portion includes user data and at least one pilot symbol.
11. The frame structure of claim 6, wherein said data portion includes user data and no pilot symbol.
12. The frame structure of claim 11, wherein said user data is transmitted in a branch I or in a branch Q.
13. The frame structure of claim 6, wherein the signature detection and the RAKE receiver assignment occurs during the time interval associated with said protection portion.
14. The frame structure of claim 10, wherein said at least one pilot symbol is transmitted on a branch I or on a branch Q.
15. The frame structure of claim 6, wherein said portion of data includes an indicator of speed.
16. The frame structure of claim 15, wherein the speed indicator is associated with a predetermined data rate and with at least one of the plurality of preselected signature patterns.
17. The frame structure of claim 15, wherein said speed indicator is included in a control portion of the random access channel.
18. The frame structure of claim 17, wherein said speed indicator is included at the start of said control portion.
19. The frame structure of claim 17, wherein said speed indicator is dispersed over said control portion.
20. The frame structure of claim 15, wherein said speed indicator is associated with a predetermined or variable length data portion.
21. The frame structure of claim 6, wherein the transmission rate of the random access channel is associated with a predetermined spreading factor.
22. The frame structure of claim 6, in wherein said portion of data is dispersed with a predetermined code associated with a predetermined mobile station.
23. 23. The frame structure of claim 6, wherein said data portion is dispersed with a predetermined code associated with a plurality of mobile stations.
24. The frame structure of claim 23, wherein the control portion of said random access channel is dispersed with a first scatter code and said data portion is dispersed with a second scatter code, said first scatter code is orthogonal with said second dispersion code.
25. The frame structure of claim 2, wherein said first and second scatter codes are each associated with a sub-tree of a code tree.
26. 26. The frame structure of claim 6, wherein a data portion of the random access channel is virtually identical to a dedicated physical channel in a mobile communication system. The frame structure of claim 6, wherein said protection portion is equal to zero. A system for use in detecting a random access request in a CDMA system, comprising: a random access detector unit (102); at least one search unit (104), an input of said system is coupled to said random access detector unit (102) and said at least one search unit (104); a control unit (106), an output of said random access control unit and said at least one search unit is coupled to said control unit; and a receiver unit RAKE (108), an output of said control unit and said input of said system is coupled to said receiver unit RAKE, wherein said output of said control unit includes a control signal comprising an order number. of a detected signature pattern, an estimated track delay and an estimated channel value. The system of claim 28, wherein said RAKE receiver unit comprises a plurality of RAKE components (108a-108n). A method for use in detecting an application random access in a CDMA system, comprising the steps of: detecting (102) a request for random access in a random access channel; searching (104) a propagation delay in a traffic channel associated with said random access channel; coupling a result of said detection step and said search step to a control unit (106); and in response to said coupling step, said control unit assigns at least one RAKE receiver component (108) to demodulate said random access request; wherein the mapping step includes coupling to said at least one RAKE receiver component of a control signal consisting of an order number for a detected signature pattern, an estimated track delay, and an estimated channel value . A random access frame structure transmitted in a random access channel from a mobile station to a mobile communication system, said random access frame structure comprising: a preamble; a portion of data; and a protection portion between said preamble and said data portion, said protection portion allows the interruption of the transmissions between the mobile terminal and the mobile communication system. The random access frame structure of claim 31, wherein said protection portion further allows the timing of the random access frame structure to be aligned with a frame segment scheme of a mobile communication system. The random access frame structure of claim 32, wherein said preamble is multiplexed I / Q. The random access frame structure of claim 31, wherein said data portion includes user data and at least one pilot symbol. The random access frame structure of claim 31, wherein the data portion includes a speed indicator associated with a predetermined transmission rate and at least one of several signature patterns preselected. The random access frame structure of claim 31, wherein a control portion of the random access channel is dispersed with a first spread code and said data portion is dispersed with a second spread code said first spread code is orthogonal with said second dispersion code. A random access frame structure transmitted in a random access channel from a mobile terminal to a mobile communication system, said random access frame structure comprising: a multiplexed I / Q multiplexed preamble by means of a preselected signature pattern; a portion of data; and a protection portion between said I / Q multiplexed preamble and said data portion, said protection portion allows the detection of said I / Q multiplexed preamble by the mobile communication system before the arrival of said portion of data thereby requiring lower regulation and minimizing the delay of random access. The random access box structure of the claim 37, wherein said data portion is virtually identical in structure to a portion of the dedicated physical uplink channel in the mobile communication system, wherein the frame structure for the random access channel and the physical uplink channel dedicated are compatible. A mobile communication system comprising: a mobile terminal for transmitting a random access frame structure in a random access channel; and a base station for receiving the random access frame structure, said random access frame structure also including: a preamble; a portion of data; and a protection portion between said preamble and said data portion, said protection portion allows interruption of the transmission between said mobile terminal and said base station. The mobile communication system of claim 39, wherein said protection portion allows the detection of said preamble by said base station before the arrival of said portion of data thereby requiring lower regulation and minimizing the delay of random access. The mobile communication system of claim 0, wherein said preamble is multiplexed I / Q and allows the compatibility of the frame structure of a random access scheme and an uplink scheme within a mobile communication system. The mobile communication system of claim 39, wherein said data portion includes a speed indicator with a predetermined transmission rate and at least one of several preselected signature patterns. The mobile communication system of claim 39, wherein a control portion of the random access channel is dispersed with a first dispersion code and said data portion is dispersed with a second dispersion code, said first dispersion code is orthogonal with said second dispersion code. A random access frame structure transmitted in a random access channel from a mobile terminal to a mobile communication system, said random access frame structure comprising: a preamble; a portion of data; and a protection portion between said preamble and said data portion, where no transmission occurs between the mobile terminal and the mobile communication system during an interval corresponding to said protection portion. The random access frame structure of claim 39 or claim 44, wherein said protection portion allows timing of the random access frame structure to align it with a frame segment scheme of the mobile communication system. The random access frame structure of claim 39 or claim 44, wherein said preamble is multiplexed I / Q. The random access frame structure of claim 44, wherein said data portion includes user data and at least one pilot symbol. The random access frame structure of claim 44, wherein said data portion includes a speed indicator associated with a predetermined transmission rate and at least one of several signature patterns preselected. The random access frame structure of claim 44, wherein a random access channel control portion is dispersed with a first spread code and said data portion is scattered with a second spread code, said first spread code is orthogonal with said second dispersion code.