KR20090005061A - Random access structure for wireless networks - Google Patents

Abstract

Apparatus and methods for accessing a wireless telecommunications network by transmitting a random access signal. The random access signal includes a random access preamble signal selected from a set of random access preamble signals constructed by cyclically shift selected root CAZAC sequences. The random access signal may be one or more transmission sub-frames in duration, the included random access preamble sequence's length being extended with the signal to provide improved signal detection performance in larger cells and in higher interference environments. The random access signal may include a wide-band pilot signal facilitating base station estimation of up-link frequency response in some situations. Each of the plurality of available random access preamble sequences may be assigned a unique information value. The base station may use the information encoded in the random access preamble to prioritize responses and resource allocations. Random access signal collisions are dealt with by a combination of preamble code space randomness and back-off procedures.

Description

A method for accessing a wireless network, a method for allocating uplink resources, and an apparatus for transmitting a random access signal {RANDOM ACCESS STRUCTURE FOR WIRELESS NETWORKS}

The present invention relates to a random access structure for a wireless network.

As wireless systems proliferate, the demand for growing user bases and new services requires the development of technologies that can meet the ever-growing expectations of users. Users of mobile communication devices expect a variety of data services, such as email, text messaging and Internet access, as well as reliable voice communications available globally.

As a result, the random access channel will include a wider range of functions than in previous or present cellular networks, thus increasing its expected load. In addition, the random access signal in which the UE initiates the random access procedure must provide Node B with sufficient information to reliably accommodate the variable cell sizes and to effectively prioritize resource requests. In addition, the random access signal should be designed to minimize interference with other UL orthogonal transmissions due to its potentially unsynchronized nature. Therefore, a more efficient random access method is needed.

Summary of the Invention

An apparatus for transmitting a random access signal, comprising: a CAZAC root sequence selector coupled to a CAZAC root sequence generator, wherein the CAZAC root sequence generator generates at least one CAZAC root sequence, and the CAZAC root sequence selector is the at least one An apparatus for autonomously selecting a preamble root sequence from a CAZAC root sequence of provides an embodiment for more efficient random access.

Another embodiment is a method of accessing a wireless network, the method comprising transmitting a signal, wherein the signal may be a method comprising a CAZAC sequence autonomously selected from a plurality of CAZAC sequences.

Another embodiment of the present invention provides a method of allocating uplink resources, comprising: receiving a signal including at least one of a selected CAZAC sequence and a wideband pilot signal from a plurality of CAZAC sequences; Analyzing the signal to estimate a frequency response of an uplink transmission channel; And allocating uplink resources based on the frequency response estimate.

DETAILED DESCRIPTION In the following detailed description, reference is made to the accompanying drawings.

1 illustrates an exemplary communications network.

2 illustrates an exemplary uplink time / frequency allocation.

3 illustrates exemplary 1 and 2 subframe random access signals.

4 shows a first embodiment of a random access signal transmitter.

5 shows a second embodiment of a random access signal transmitter.

6 shows a third embodiment of a random access signal transmitter.

7 illustrates an exemplary asynchronous random access signal receiver.

8 is a flow diagram of an exemplary random access preamble signal length adjustment and transmission method.

9 is a flow diagram of an exemplary alternative random access preamble signal length adjustment and transmission method.

10 is an exemplary conventional random access procedure signal flow diagram.

11 is an alternative exemplary conventional random access procedure signal flow diagram.

12 is an exemplary hybrid random access procedure signal flow diagram.

13 is a flow diagram of an example random access collision processing method.

14 illustrates an orthogonality principle used in an orthogonal frequency division multiplexing system.

15 illustrates a misalignment between a random access preamble signal and scheduled data OFDM symbols.

FIG. 16 illustrates alternative exemplary 1 and 2 subframe random access signals. FIG.

The drawings show embodiments that will be described in detail. However, the description and the appended drawings are not intended to limit the claimed invention to the embodiments, but to disclose and protect all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.

Various systems and methods are described herein using a random access channel in a communication system. Disclosed apparatus and methods

An apparatus for transmitting and receiving random access signals;

Improving uplink resource allocation using a random access preamble signal or a wideband pilot signal in the random access signal;

Encoding information in the random access signal by selecting random access preamble signals or frequency bands;

An uplink resource allocation method using information encoded in a random access preamble signal or frequency bands;

A method for enabling fast load balancing using information encoded in a random access preamble signal or frequency bands;

Adapting the random access signal to variable cell sizes, noise, interference conditions, etc. by extending the random access preamble signal lifetime;

A method of optimizing the number of recognizable random access attempts for a given time frequency radio resource;

A method of minimizing interference between random access and scheduled access;

Adapting prime length random access preamble signals for use in random access signals; And

Random access signal collision recovery method

It includes.

Embodiments of the present invention generally relate to a wireless communication system and can be used to generate random access transmissions. Random access transmission means transmission by a mobile terminal of at least one signal from a plurality of predefined signals. The plurality of predefined signals is specified by a random access structure. A mobile terminal may also be referred to as user equipment (“UE”) and may generally be a fixed or portable wireless device, a cellular phone, a personal digital assistant, a wireless modem card, or the like. Random access transmissions may be referred to as ranging transmissions or other similar terms.

User equipment may be uplink (“UL”) synchronized or not UL synchronized. If the UE UL is not time synchronized or loses time synchronization, the UE performs asynchronous random access to request allocation of uplink resources. The UE may also perform asynchronous random access to register itself with the access point or for various other reasons. Possible uses of random access transmission are various and do not limit the scope of the present invention. For example, asynchronous random access allows an access point (“Node B”) to estimate the transmission timing of the UE, adjust it if necessary, as well as allocate resources for subsequent uplink transmission of the UE. . Resource requests from UL asynchronous UEs may occur for a variety of reasons, for example for new network access, data ready for transmission or handover procedures. In general, Node B is a fixed station and may be referred to as a known transceiver system (BTS), access point, base station or various other names.

1 illustrates an example wireless communication network. The communication network needs to include more base stations in operation, but the exemplary communication network includes base stations 101, 102, 103. Each of the base stations 101, 102, 103 is operable on corresponding coverage areas 104, 105, 106. The coverage area of each base station is further divided into cells. In the illustrated network, the coverage area of each base station is divided into three cells. A handset or other UE 109 is shown in cell A 108 within coverage area 104 of base station 101. The base station 101 is transmitting and receiving transmissions with the UE 109. When the UE 109 moves from cell A 108 to cell B 107, the UE 109 can be handed over to the base station 102. Since the UE 109 is synchronized with the base station 101, the UE 109 may initiate a handover to the base station 102 using asynchronous random access.

The asynchronous UE 109 also requests allocation of uplink 111 time or frequency or code resources using asynchronous random access. When the UE 109 has data ready to transmit, such as traffic data, measurement reports, tracking area updates, etc., the UE 109 may transmit a random access signal on the uplink 111. The random access signal informs the base station 101 that the UE 109 needs uplink resources to transmit the UE's data. The base station 101 responds by sending a message to the UE 109 via the downlink 110 that includes parameters of resources allocated for UE 109 uplink transmission with possible timing error correction. After receiving the resource allocation and possible timing progress message sent by the base station 101 via the downlink 110, the UE 109 (possibly) adjusts its transmission timing and allocates the allocated resource for a predetermined time interval. To transmit data on the uplink 111.

2 shows an example uplink transmission frame 202 and allocation of frames for the scheduled access channel and the random access channel. Exemplary uplink transmission frame 202 includes a plurality of transmission subframes. Subframes 203 are reserved for scheduled UE uplink transmissions. Between the scheduled subframes 203, time and frequency resources allocated to the random access channels 210 are interspersed. In the example of FIG. 2, a single subframe supports two random access channels. Note that the illustrated number and spacing of random access channels is a matter of convenience, and that a particular transport frame implementation may allocate more or less resources to random access channels. Including multiple random access channels allows multiple UEs to transmit random access bursts simultaneously without collisions. However, since each UE independently selects the random access channel it transmits, collisions may occur between the UE random access signals. This conflict requires resolution.

3 illustrates one embodiment of a random access signal. The random access signal 301 occupies a single subframe 308, and the random access signal 311 occupies two subframes. In an embodiment of one subframe random access signal 301, the duration 302 is used to prevent interference between the random access preamble signal 304 and any transmission on the random access preamble signal frequency bands during the previous subframe. It is included before the transmission of the random access preamble signal 304. The duration 302 whose details are no longer relevant to the novelty of the present invention may or may not be implemented as a cyclic prefix appended to the start of the preamble to permit simple frequency domain receiver implementation. The random access preamble signal 304 follows the duration 302. The random access preamble signal 304 is designed to maximize the likelihood of preamble detection by Node B, while minimizing the likelihood of false preamble detections by Node B, while maximizing the total number of resource opportunities.

Embodiments of the present invention generate a random access preamble signal using constant amplitude zero autocorrelation (“CAZAC”) sequences. CAZAC sequences are complex-valued sequences with two characteristics: 1) constant amplitude (CA) and 2) zero cyclic autocorrelation (ZAC). Known examples of CAZAC sequences include (but are not limited to) Chu sequences, Frank-Zadoff sequences, Zadoff-Chu (ZC) sequences, and generalized Chirp-Like (GCL) sequences.

As is known in the art, as follows, i.e.

For odd N, a _M (k) = exp [j2π (M / N) [k (k + 1) / 2 + qk]]

For even _{N, a M (k) =} exp [j2π (M / N) [k 2/2 + qk]]

Zadoff-Chu (“ZC”), as defined as, is a representative example of CAZAC sequences. In the above formula, "M" and "N" are relatively prime, and "q" is any constant integer. "N" is the length of the sequence, "k" is the index of the sequence element, and "M" is the index of the root ZC sequence. Making "N" a prime maximizes the set of non-orthogonal root ZC sequences with optimal cross correlation. Thus, when "N" is a prime number, there are "(N-1)" possible choices for "M", each choice resulting in a different root ZC CAZAC sequence. In the present disclosure, the terms Zadoff-Chu, ZC and ZC CAZAC are used interchangeably. The term CAZAC refers to any CAZAC sequence, ZC or vice versa.

In the main embodiment of the present invention, the random access preamble signal 304 (or 314) is constructed from a CAZAC sequence, such as a ZC sequence. Further changes to the selected CAZAC sequence using one of the following operations: multiplication by complex constant, DFT, IDFT, FFT, IFFT, cyclic shifting, zero padding, sequence block repetition, sequence truncation, sequence cyclic extension, etc. Can be performed. Thus, in the main embodiment of the present invention, the UE selects a CAZAC sequence, presumably applies a combination of desired changes to the selected CAZAC sequence, modulates the modified sequence, and wirelessly transmits the resulting random access signal to the random access preamble signal. Configure 304 or 314.

In practical systems, it is necessary to specify or predefine a set of allowed random access preamble signals. Thus, the UE autonomously selects (or can be assigned) at least one random access preamble signal 304 or 314 from a predefined set of random access preamble signals. The UE then wirelessly transmits the selected signal. Node B searches within a finite set of predefined random access signals, and thus can detect the occurrence of a random access transmission by the UE.

One way to predefine a set of random access preamble signals is to allow selection of changes to a fixed root CAZAC sequence, such as a ZC CAZAC sequence. For example, in one embodiment of the present invention, when performing a change of the root CAZAC sequence, different random access preamble signals are constructed by applying different cyclic shifts. Thus, in this embodiment of the present invention, the UE autonomously selects the random access preamble signal by selecting the value of the cyclic shift. The value of the selected cyclic shift is applied during the change process of the root CAZAC sequence. For the sequence [c (0) c (1) c (2) ... c (L-1)], the corresponding cyclically shifted sequence is [c (n) c (n + 1) c (n + 2). ) ... c (L-1) c (0) c (1) ... c (n-1)], where "n" is the value of the cyclic shift. Thus, in this embodiment, the set of possible cyclic shifts defines a set of random access preamble signals that are allowed.

An alternative way to pre-define a set of random access preamble signals is to allow selection of applicable root CAZAC sequences, such as a ZC sequence. For example, in this embodiment of the present invention, different random access preamble signals are constructed by applying predefined common changes to different root CAZAC sequences. As a result, the UE selects and then changes the random access preamble signal by selecting different root CAZAC sequences to generate the random access preamble signal. Thus, in this alternative embodiment of the invention, the set of allowed root CAZAC sequences also defines a set of allowed random access preamble signals.

In a general embodiment of the present invention, the set of allowed random access preamble signals is defined by two different sets: 1) a set of allowed root CAZAC sequences and 2) a set of allowed changes for a given root CAZAC sequence. . For example, in this general embodiment of the present invention, the random access preamble signal is constructed by first selecting the root ZC CAZAC sequence and then selecting the value of the cyclic shift. The selections can be performed autonomously by the UE, the UE applying the selected value of the cyclic shift during the change process of the selected root ZC CAZAC sequence.

4 is a block diagram illustrating an apparatus according to an embodiment of the present invention. Device 400 includes a ZC root sequence selector 401, a cyclic shift selector 402, a repeat selector 403, a ZC root sequence generator 404, a cyclic shifter 405, a DFT 406, a tone map 407. , Other signals or zero padding 411, IDFT 408, repeater 409, optional repeat samples 412, additional CP 410, and random access signal 413. Elements of the apparatus may be implemented as components in a fixed or programmable processor. In certain embodiments, IDFT block 408 may be implemented using fast Fourier inverse transform (IFFT), and DFT block 406 may be implemented using fast Fourier transform (FFT). Apparatus 400 is used to select and perform random access preamble signal transmissions as follows. The UE performs the selection of the ZC CAZAC route sequence using the ZC root sequence selector 401 and the selection of the cyclic shift value using the cyclic shift selector 402. The UE then generates a ZC sequence using the ZC route sequence generator 404. Then, if necessary, the UE uses the cyclic shifter 405 to perform cyclic shifting of the selected ZC sequence. The UE performs Discrete Fourier Transform (DFT) of the cyclically shifted ZC sequence at DFT 406. The result of the DFT operation is mapped to the set of designated tones (subcarriers) using the tone map 407. Additional signals or zero padding 411 may or may not be present. The UE then uses IDFT 408 to perform IDFT of the mapped signal. The size of the IDFT 408 may optionally be larger than the size of the DFT 406. Block repetition of the IDFT processed signal is optional and performed using 409. Note that the repeated signals 412 represent optional repeat samples. This repetition may be applied when the preamble transmission occupies two or more subframes. An optional cyclic prefix (CP) may be added using 410 to reach the random access signal 413. The random access signal 413 is wirelessly transmitted.

5 is a block diagram illustrating an apparatus according to an alternative embodiment of the present invention. The apparatus 500 includes a ZC route sequence selector 501, a cyclic shift selector 502, a repeat selector 503, a ZC route sequence generator 504, a cyclic shifter 505, a DFT 506, a tone map 507. , Other signals or zero padding 511, IDFT 508, repeater 509, optional repeat samples 512, additional CP 510, and random access signal 513. Elements of the apparatus may be implemented as components in a fixed or programmable processor. In certain embodiments, IDFT block 508 may be implemented using fast Fourier inverse transform (IFFT), and DFT block 506 may be implemented using fast Fourier transform (FFT). Apparatus 500 is used to select and perform a random access preamble signal transmission as follows. The UE performs the selection of the ZC CAZAC route sequence using the ZC root sequence selector 501 and the selection of the cyclic shift value using the cyclic shift selector 502. The UE then generates a ZC sequence using the ZC route sequence generator 504. The selected ZC sequence is transformed using the DFT 506. The result of the DFT operation is then mapped to the set of designated tones (subcarriers) using the tone map 507. Additional signals or zero padding 511 may or may not be present. The UE then performs IDFT of the mapped signal using 508. Using the cyclic shifter 505, the value of the selected cyclic shift is applied to the IDFT processed signal. The value of the cyclic shift is obtained from the cyclic shift selector 502. Block repetition of the IDFT processed and cyclically shifted signal is optional and performed using iterator 509. Note that 512 represents optional repeated samples. This repetition may be applied when the preamble transmission occupies two or more subframes. Subsequently, an optional cyclic prefix (CP) may be added using 510 to reach the random access signal 513. The random access signal 513 is wirelessly transmitted.

6 is a block diagram showing an apparatus according to a third embodiment of the present invention. The apparatus 600 may include a ZC root sequence selector 601, a cyclic shift selector 602, a repeat selector 603, a ZC root sequence generator 604, a cyclic shifter 605, a tone map 607, other signals, or Zero padding 611, IDFT 608, repeater 609, optional repeat samples 612, additional CP 610, and random access signal 613. Elements of the apparatus may be implemented as components in a fixed or programmable processor. In certain embodiments, IDFT block 608 may be implemented using fast Fourier inverse transform (IFFT). Apparatus 600 is used to select and perform random access preamble signal transmissions as follows. The UE performs the selection of the ZC CAZAC route sequence using the ZC root sequence selector 601 and the selection of the cyclic shift value using the cyclic shift selector 602. The UE then generates a ZC sequence using the ZC root sequence generator 604. The selected ZC sequence is mapped to a set of designated tones (subcarriers) using tone map 607. Additional signals or zero padding 611 may or may not be present. The UE then performs IDFT of the mapped signal using 608. Using cyclic shifter 605, the value of the selected cyclic shift is applied to the IDFT processed signal. The value of the cyclic shift is obtained from the cyclic shift selector 602. Block repetition of the IDFT processed and cyclically shifted signal is optional and performed using 609. Note that 612 indicates optional repeated samples. This repetition may be applied when the preamble transmission occupies two or more subframes. Then, an optional cyclic prefix (CP) may be added using 610 to arrive at the random access signal 613. The random access signal 613 is wirelessly transmitted.

In various embodiments of the present invention, the set of allowed cyclic shifts may be sized according to the cell's physical limitations, including cell maximum round trip delay plus delay spread of the channel. For example, a single root ZC CAZAC sequence may be cyclically shifted by any integer multiple of the cell's maximum round trip delay plus delay spread to produce a set of predefined random access preamble signals. The maximum round trip delay plus delay spread of the channel requires conversion of the sequence to sampling units. Thus, given the maximum round trip delay plus delay spread of the channel as " x ", the possible choices of cyclic shift values can be sized as n from {0, x, 2x, ..., (u-1) x}. Where ux cannot exceed the length of the sequence being cyclically shifted.

Round trip delay is a function of cell size, and cell size is defined as the maximum distance d that a UE can interact with a cell's base station, and can be approximated using equation t = 6.67d, where t and d are μs and km Respectively. Round trip delay is the delay of the faster radio path. An exemplary faster path is a gaze path defined as a direct (straight) radio path between the UE and the base station. When a UE is surrounded by reflectors, its radiation is reflected by these obstacles, creating a number of longer mobile radio paths. As a result, multiple time delay copies of the UE transmission arrive at the base station. The period over which these copies are delayed is referred to as "delayed spreading", for example 5 μs can be considered its conservative value in certain instances.

If the set of cyclic shifts {0, x, 2x, ..., (u-1) x} generates an insufficient number of different random access preamble signals, additional root CAZAC sequences (for random access preamble signal generation) For example, for M = 2 and M = 3) can be used. In this situation, the choice of prime N proves beneficial because the set of possible choices for M with respect to N primes is {1, 2, ..., (N-1)}. Thus, in one embodiment of the present invention, different random access preamble signals are identified by the set of possible choices for the cyclic shift value and the set of choices allowed for M. In addition to providing auxiliary intra-cell sequences, when used in neighboring cells, these additional root ZC CAZAC sequences provide good inter-cell interference mitigation. Thus, during cellular system design, a scenario in which adjacent cells use the same root sequences should be avoided. This may be accomplished through a number of possible techniques, including but not limited to cellular system planning, sequence hopping, or a combination thereof.

The set of licensed random access preamble signals is known to the UE prior to random access transmission. This can be accomplished in a number of different ways, including hardwiring such information at the UE. However, the preferred approach is to broadcast information that allows Node B to infer the set of random access preamble signals that the UE is allowed to. For example, Node B may broadcast 1) which root CAZAC sequences are allowed and 2) which "cyclic shift" values are allowed. The UE reads the broadcasted information, infers a set of allowed random access preamble signals, selects at least one signal from the set, and performs random access transmission. Note that the selection of the random access preamble signal corresponds to the selection of the root ZC CAZAC sequence, the selection of the cyclic shift value, and possibly the selection of the frequency bins (when multiple bins are configured per random access time slot). In certain cases, additional broadcast information may be added, such as whether the UE needs to perform signal repetition. In general, this approach based on the broadcasting of additional information is preferred in that it can optimize the cellular network based on physical constraints such as cell size. In addition, any given UE is flexible enough to be used in all types of cells and system optimization is achieved by cell design.

Sequences obtained from cyclic shifts of a single CAZAC root sequence (ZC or vice versa) are orthogonal to each other when the cyclic shift value is greater than the maximum time uncertainty of the received signal including delay spread and spill-over. That is, cyclic shifts produce regions with zero correlation between different random access preamble signals. Thus, a cyclically shifted sequence can be observed without any interference from sequences generated using different cyclic shifts. Sequences obtained from cyclic shifts of different Zadoff-Chu (ZC) sequences are not orthogonal, but have an optimal cross correlation when the sequence length is prime. Thus, in various embodiments, orthogonal sequences are preferred over non-orthogonal sequences. Because of this, additional Zadoff-Chu (ZC) root sequences can be used if the required number of sequences cannot be generated by the cyclic shifts of a single root sequence. As a result, cyclic shift size determination is very important in random access sequence design. As mentioned above, the cyclic shift value is sized to resolve the maximum time uncertainty in random access preamble reception. This time uncertainty reflects Node B-UE-Node B signal propagation delay ("round trip delay") plus delay spread. Thus, cyclic shift size determination ensures that different random access signals generated from a single root CAZAC sequence are received within the area of zero cross correlation. Although delay spread can be assumed to be constant, the signal round trip time depends on the cell size. Thus, the larger the cell, the larger the cyclic shift used to generate the orthogonal sequences, and thus the larger the number of Zadoff-Chu (ZC) root sequences used to provide the required number of sequences.

Table 1 provides an example of random access preamble sequence design for different cell sizes. Table 1 shows how the number of root ZC CAZAC sequences increases from 1 to 8 when the cell size increases from 0.8 km (cell scenario 1) to 14 km (cell scenario 4). Table 1 is derived using the following parameters: maximum delay spread is 5 μsec, root ZC CAZAC sequence length is 863 samples, preamble sampling rate is 1.07875 MHz, and spillover guard period is 2 samples. . Since the expected inter-cell interference and load (user density) increase as the cell size decreases, small cells need protection from more co-preamble interference than large cells. Therefore, the relationship between cell size and the number of required Zadoff-Chu (ZC) root sequences takes into account system optimization and Node B should configure the primitive cyclic shift to be used independently in each cell. The set of cyclic shift values to be used is then constructed as integer multiples of the raw cyclic shift value. As shown in Table 1, the system can be optimized by setting the raw cyclic shift value or by setting the number of different root Zadoff-Chu (ZC) sequences to be used in the cell. This setup possibility advantageously provides a certain number of different random access preamble signals regardless of cell size, which simplifies the specification of the medium access control (MAC) procedure.

Table 1: Cell Scenarios for Different Cyclic Shift Increments

Cellular Scenario Index Cell size [km] Number of different random access preamble signals Number of root ZC CAZAC sequences used Number of cyclic shifts used per ZC sequence Raw cyclic shift value ([sample] One 0.8 64 One 64 13 2 2.6 64 2 32 26 3 6.3 64 4 16 53 4 13.9 64 8 8 107

7 shows a random access signal receiver. This receiver advantageously uses the time and frequency domain transform components used to map and demap data blocks within an uplink subframe. The received random access signal 701, including the cyclic prefix and the random access preamble signal, is input to a cyclic prefix removal component 702 that removes the cyclic prefix from the random access signal generation signal 703. The frequency domain transform component DFT 704 is coupled to the cyclic prefix cancellation component 702. The frequency domain transform component 704 converts the signal 703 into subcarrier mapped frequency tones 705. The subcarrier demapping component 706 is coupled to the frequency domain transform component 704. Subcarrier demapping component 706 demaps subcarrier mapped frequency tones 705 to generate useful frequency tones 707. The multiplication component 711 is coupled to both the subcarrier demapping component 706 and the frequency domain transform component 709. A frequency domain transform component (DFT) 709 transforms a preamble root sequence 710, such as a fractional length Zadoff-Chu sequence, into a set of corresponding pilot frequency tones 708. Complex conjugation of the pilot frequency tones 708 using 721 is performed to generate samples 720. Multiplication component 711 generates a set of frequency tones 712 by performing a tone by tone complex multiplication of the received frequency tones 707 and samples 720. A time domain transform component (IDFT) 713 is coupled to the multiplication component 711. The time domain transform component 713 converts the multiplied frequency tones 712 into a correlated time signal 714. Correlated time signal 714 includes concatenated power delay profiles of cyclic shift copies of preamble root sequence 710. The energy detection block 715 is coupled to the time domain transform block 713. The energy detection block 715 identifies the received preamble sequences by detecting the time of peak correlation between the received random access signal 701 and the preamble root sequence 710. Note that the frequency domain conversion component 709 is required when using the transmitters shown in FIG. 4 or 5. The frequency domain transform component 709 can be omitted when using the transmitter of FIG. 6.

As disclosed, it is recommended that a fraction length preamble sequence be used in the uplink transmitter system. The fractional length preamble sequence may be configured as follows. The preamble duration Tp is selected to optimize cell coverage (cell size, noise and interference conditions) and to be an integer multiple of the uplink data block duration. Reference length Npi = Tp x Rsi samples are selected, where Rsi is the allocated random access signal bandwidth and is not used by data transmissions. Subsequently, a preamble sequence having a sequence length corresponding to the largest fraction Np smaller than the reference length Npi is generated. Therefore, since the preamble duration is maintained at Tp, the preamble sampling rate is Rsi x Np / Npi. Since Npi subcarriers are allocated to the random access channel, and the preamble has been shortened to the nearest lower fraction (Np) of samples, an unused sub that can be zeroed and distributed outside the preamble subcarriers to isolate the preamble from the surrounding frequency bands. Carriers are present.

8 is a flow diagram of an example method of adapting a fractional length sequence for use in an uplink transmitter. At 802, the preamble duration Tp is selected. Tp is an integer multiple of the uplink subframe data block duration. At 804, a reference length is derived. This reference length is Npi samples, where Npi = Tp x Rsi, where Rsi is the random access signal bandwidth. At 806, the reference length derived at 804 is shortened to the nearest lower prime number Np of samples to derive the preamble sequence length. At 807, a sequence of Np lengths is generated. At 808, Np time samples are converted to Np frequency tones. At 810, Np frequency tones are mapped to assigned random access channel subcarriers. Npi-Np subcarriers remain unused since Npi subcarriers are allocated to the random access signal, and the preamble sequence length is shortened to Np samples, so that only Np frequency tones are mapped to the subcarriers. At 812, unused subcarriers are zeroed and distributed around the preamble subcarriers to provide isolation from adjacent frequency bands. These unused subcarriers can potentially be reused for cubic metric reduction through cyclic extension or tone reservation.

9 shows a flowchart of an alternative method of generating a fraction length sequence for use in an uplink transmitter. Since the preamble sequence is deterministic, decimal length preamble sequences can be predefined and stored for subsequent use. At 902, if configured by Node B, fractional length preamble sequences are generated and converted into frequency domain preamble samples. At 904, frequency domain preamble samples are stored in a storage device so that they can be received as needed. At 906, random access signal transmission is initiated and the preamble duration is selected. The selected duration is an integer multiple of the uplink subcarrier data block duration and is selected to satisfy the system coverage requirements. At 908, the stored preamble sequence is selected. The selected sequence is preferably a sequence having a few samples that are just below the number of samples calculated from the lifetime and random access signal bandwidth selected at 906. At 910, preamble frequency samples are read from the storage device and mapped to subcarriers assigned to the random access channel. Since more subcarriers are allocated than preamble frequency samples are present, unused subcarriers are zeroed and distributed around the preamble subcarriers to provide isolation from adjacent frequency bands. This alternative implementation allows for omission of the frequency domain conversion component 406 from the random access preamble transmitter. The preamble samples are frequency domain converted only once before storage, so the conversion process is independent of the latency requirements of the random access preamble transmitter and can be implemented simpler and at lower cost. It should also be noted that the frequency domain transform component 406 may be completely removed if the preamble root sequence is configured directly in the frequency representation by Node B. However, since the preamble sequence is defined to be a cyclically shifted Zadoff-Chu sequence, a cyclic shift is performed. Cyclic shift may be performed at a system sampling rate prior to cyclic prefix insertion 410.

14 illustrates the principle of orthogonal multiplexing in orthogonal frequency division multiplexing (“OFDM”) systems. Each tone has a modulated symbol according to the frequency overlap time limited orthogonal structure. The frequency tones overlap each other, so that the spectral envelopes of the surrounding tones at the center of one tone are null. This principle allows multiplexing different transmissions in an orthogonal manner at the same system bandwidth. However, this remains true only if the subcarrier spacing δf remains constant. δf is equal to the inverse of the OFDM symbol lifetime (T) used to generate frequency tones by the DFT. Since the preamble OFDM symbol is longer than the data OFDM symbol, the subcarrier interval of the preamble OFDM symbol will be shorter than the subcarrier interval of the data OFDM symbol. In addition, since the data and preamble OFDM symbols are neither aligned nor have the same duration (Figure 15), exact orthogonality cannot be achieved. However, the design rules below aim to minimize mutual interference between preamble and data OFDM symbols. First, setting the preamble OFDM symbol lifetime to an integer multiple of the data symbol lifetime provides some equal unitability between the preamble and the data subcarriers, thus reducing the interference of these subcarriers. Second, the preamble sampling frequency should be an integer multiple of the data symbol subcarrier spacing.

In OFDM systems, transmissions of different UEs are dynamically allocated to different non-overlapping frequency bands. This allocation is based on a minimum frequency granularity, commonly referred to as a resource block (RB). In order to facilitate frequency multiplexing of the random access preamble and data transmission, the preamble is preferably assigned an integer number of resource blocks.

In addition to the detection process, random access preamble signal 304 enables base station 101 to analyze the frequency response of uplink 111 over a range of frequencies within the preamble bandwidth. Characterization of the uplink frequency response enables the base station 101 to adjust the narrowband uplink 111 resources allocated to the UE 109 within the preamble bandwidth to match the uplink 111 frequency response, thus Enable uplink resources to be used more efficiently

16 is a random designed to solve a situation in which the ratio between the random access preamble signal bandwidth and the first post-preamble uplink transmission is too small to adequately benefit from sounding the channel using only the random access preamble signal itself. An alternative embodiment of the access signal is shown. Both one subframe random access signal 1601 and two subframe random access signal 1621 are shown. The addition of the wideband pilot signal 1610 to the random access signal 1601 allows the base station 101 to analyze the frequency response of the uplink 111 over a wider frequency range than is possible using only the random access preamble signal. do.

In the illustrated embodiment, the cyclic prefix 1608 is followed by the random access preamble signal 1604. The cyclic prefix 1608 includes a guard interval designed to remove interference between the random access preamble signal 1604 and the wideband pilot signal 1610.

Guard interval 1612 is followed by wideband pilot signal 1610 to prevent interference between wideband pilot signal 1610 and any transmission in subsequent subframes on the same transmission frequencies used by wideband pilot signal 1610. .

The random access signal 1621 occupies two subframes 1634. The random access signal 1621 is structurally similar to the random access signal 1601, but the random access preamble signal 1624 extends to occupy most of the two subframes. This extension may be accomplished by repeating one subframe random access preamble signal 1604 or by extending the CAZAC sequence. Guard interval 1622 precedes random access preamble signal 1624 and cyclic prefix 1628. The wideband pilot signal 1630 and the guard interval 1632 follow the random access preamble signal 1624 to complete the two frame random access signal 1621.

Referring again to FIG. 3, the guard interval 306 is followed by the random access preamble signal 304 so that the random access preamble signal 304 and subsequent subs on the same transmission frequencies used by the random access preamble signal 304. Prevents interference between any transmission in the frame.

In FIG. 3, the 2 subframe random access signal 311 may include a guard interval 312 that may include a cyclic prefix to prevent inter-symbol interference between the subsequent random access preamble signal 314 and any transmission in the previous subframe. Begins with). The random access preamble signal 314 extends into a second subframe. This extension can be done by concatenating multiple copies of one subframe random access preamble signal 304 or by generating the random access preamble signal 314 as an extended CAZAC sequence, thus obtained by cyclically shifting the root CAZAC sequence. The number of orthogonal CAZAC sequences can be kept nearly constant. Although two subframe random access signals are illustrated, random access signals including any number of subframes needed to accommodate a particular cell size and noise, interference condition can be similarly configured. In the embodiment shown in FIG. 3, the guard interval 318 follows the random access preamble signal 314 to complete the two subframe random access signal 311.

In certain embodiments, it is desirable to transmit certain information as part of a random access procedure to assist in scheduling subsequent UE transmissions of the base station. The random access cause, UE identifier, required capacity, and downlink radio link quality indicator (eg, channel quality indicator "DL CQI" or path loss) are examples of information potentially useful to the base station when included in the random access procedure. . 10 and 11 illustrate two conventional approaches to transmitting data during random access. In FIG. 10, the UE 1001 transmits a random access signal 1003. The random access signal 1003 is extended to include information useful to the Node B 1002. Node B 1002 responds with timing information 1004 for adjusting uplink timing of UE 1001 and uplink resource allocation 1005 for UE 1001 to use for subsequent uplink data transmission 1006. do.

In FIG. 11, the UE 1101 transmits a random access signal 1103 without additional information. Node B 1102 responds with uplink resource allocation 1104 and timing information to be used by subsequent scheduling request 1105. The UE 1101 sends a scheduling request 1105 using the allocated uplink resources, and the Node B 1102 responds by sending an uplink resource allocation 1106. UE 1101 uses the allocated uplink resources for subsequent uplink data transmission 1107.

The procedure of FIG. 10 exhibits lower latency than the procedure of FIG. However, to achieve an acceptable error rate, the information message contained within burst 1003 may be many times longer than the preamble. Thus, the procedure of FIG. 10 causes higher overhead than the procedure of FIG. Finally, when the efficiency of the scheduled channel is higher than the contention channel, the procedure of FIG. 11 may be desirable.

12 illustrates a novel embodiment of a random access procedure in which the UE 1201 transmits a random access signal that implicitly includes information related to the determination of the Node B 1201. The information of 1201 is not explicitly transmitted as in the procedure of FIG. 10 but is encoded by, for example, selection of a preamble sequence and a transmission band. For example, if UE 1201 encodes a 3-bit random access cause, i.e. 2-bit DL CQI and 1 random bit in the random access signal, this information is encoded in any 2 ⁶ unique combinations of random access preamble signals. Can be. Additional combinations may be provided by allocating multiple frequency bands 201 for random access. Node B 1202 uses the encoded information when receiving random access signal 1203, for example, to determine a response to a resource request. The determined response may be based on downlink channel quality, urgency of resource request, certain uplink allocation based on random access cause or other appropriate criteria. Node B 1202 responds to random access signal 1203 with timing information and scheduling request resource allocation 1204 as appropriate. The UE 1201 transmits the scheduling request 1205 using the transmission resource allocated in the message 1204. Upon receipt of scheduling request 1205, Node B 1202 sends uplink resource allocation 1206, and UE 1201 performs subsequent data transfer 1207 on the allocated resources. In another embodiment, the procedure of FIG. 10 is used, but as described above in this paragraph, it is used with information encoded by selection of random access signal parameters such as a random access preamble signal or frequency band, and thus, of FIG. Inefficiencies in the procedure can be avoided and the reduced latency of the procedure in FIG. 10 can be used.

Encoding of the random access cause in the random access signal enables the implementation of selective access restrictions based on the cause of the random access. For example, in a high load cell, Node B may accept the UE's random access attempts related to handover or emergency calls, but reject the random access attempts for the initial access. This example illustrates the strict restriction that new users are rejected based on cell load. However, flexible restrictions are also possible that allow for approval of new users based on link quality. Enabling selective access restrictions based on the random access cause encoded in the random access signal allows implementation of fast and efficient load balancing at the physical layer, reducing the latency associated with load balancing implemented at higher layers.

In order to support load balancing according to the present invention, the random access procedure supports the following features, i.e. 1) the random access signal includes a random access cause, and 2) the Node B in the random access response is NACK (non- acknowledgment) to reject the request of the UE.

As a further refinement of the disclosed implicit information encoding method, a group of signatures in which 2 ⁶ combinations of random access preamble signals (“signatures”) used to encode the information assist usage with similar response priority or latency requirements. Can be subdivided into In one embodiment, 64 available signatures may be divided into 6 groups (“access type”). Access types may be, for example, handover type 1, high priority UE connection, handover type 2, normal priority UE. Connections, asynchronous recovery with uplink allocation requests, and timing progress maintenance without uplink allocation requests, each access type representing a different access priority and urgency, and thus a corresponding latency request. Can use a different number of signatures, and access types that require lower latency can be assigned a larger number of signatures.The number of signatures assigned to each access type can be accessed based on, for example, cell load. It can be dynamically configured within each cell to optimize type signature diversity.

Additional information, for example DL CQI, may be encoded within the signatures of the access type by selecting subgroups of signatures to represent information values. For example, if sixteen signatures are assigned to handover type 1, these signatures can be divided into two subgroups of eight signatures each, with each subgroup representing one state of one information bit. .

In another embodiment, the 64 available signatures are divided into two cause groups: emergency causes (eg, handover, new data to send in RRC_CONNECTED state) and non-emergency causes (eg, initial access, tracking). Region update). A fair split would consist in assigning each group a number of signatures corresponding to each load in each group. However, unfair partitioning may be used to support emergency causes (more signatures) than non-emergency causes (less signatures). Moreover, the emergency causes can be further divided into two subpartitions to have one bit, for example radio link quality. Node B uses this information when assigning a UL grant for a first UL transmission on a shared channel. Thus, a UE with an emergency cause in good radio link conditions can potentially send its complete random access request in one message, which further speeds up the procedure.

It is desirable to avoid collisions in the random access channel. Signature diversity is a major means of avoiding collisions. However, when collisions occur, they need to be resolved. Collisions can be resolved by, for example, a combination of back-off procedures and signature spatial randomness. As discussed above, access types that require lower latency should be assigned a larger number of signatures to reduce the likelihood of collisions when signatures are randomly selected. In addition, when assigning signatures to each access type, the expected load of each access type is taken into account. For example, by reducing the load, the rearrangement of the list of six access types described above can be achieved by handover type 1, asynchronous recovery with uplink allocation request, timing progress maintenance without uplink allocation request, handover type 2, high priority There may be a priority UE connection and a normal priority UE connection. The assignment of signatures, taking into account both latency and load, can be the following signature assignments: handover type 1-16 signatures, maintaining timing progress without uplink assignment requests-asynchronous recovery with 16 signatures, uplink assignment requests- 12 signatures, high priority UE connection-8 signatures, handover type 2-8 signatures, and normal priority UE connection-4 signatures.

When one access type is applicable to both competitive and non-competitive access, the relevant signatures may be assigned some to randomness and some to non-competitive use.

Since conflict resolution through backoff procedures increases latency, backoff procedures should only be used with random signature selection if inevitable. 13 is a flow diagram of an example conflict resolution method incorporating both backoff and randomness in signature space. At 1302, an unscheduled transmission procedure is initiated by zeroing a counter that maintains the number of collisions detected. At 1304, one signature is randomly selected from the pool of available signatures. The next occurring random access time slot is identified at 1306 and a random access signal is sent at 1308. If Node B detects a collision at 1310 and sends a NACK to the UE, or if Node B fails to detect a random access signal due to a collision at 1312 and no response is received by the UE, the collision counter is incremented at 1318. If fewer collisions are registered at 1320 than the predetermined maximum number of collisions, the transmission is restarted with a random signature selection at 1304.

If the random access signal sent at 1308 is not NACKed by Node B at 1310, and a response including resource allocation is received from Node B at 1312, the UE transmits its data on the allocated resource at 1314. If a collision occurred during the transmission of the random access signal of 1308, but the Node B fails to detect the collision and transmits a single resource allocation for use by multiple UEs, the UE transmission of 1314 will collide. When such a collision is detected by the UE at 1316, the collision counter is incremented at 1318, and if less than a predetermined maximum number of collisions have been registered at 1320, transmission is restarted with a random signature selection at 1304.

If the predetermined maximum number of collisions is registered at 1320, the backoff procedure is initiated at 1322. The predetermined maximum number of collisions may vary for each access type. The backoff delay may also vary from access type to access type. In one embodiment, the backoff delay is a function of the number Nu of previously unsuccessful attempts, so the first attempt after backoff occurs with a probability (2/3) ^Nu in the next random access time slot.

The first embodiment of the present invention includes a random access signal transmission apparatus including a CAZAC route sequence selector coupled to a CAZAC route sequence generator, wherein the CAZAC route sequence generator generates at least one CAZAC route sequence, and CAZAC The root sequence selector selects a preamble root sequence from at least one CAZAC root sequence. The CAZAC root sequence generator is also a Zadoff-Chu sequence generator. The apparatus may further comprise a sequence changer coupled to the CAZAC root sequence generator to change the preamble root sequence, and a sequence change selector coupled to the sequence changer to select the preamble root sequence change. The sequence changer may also be a cyclic shifter. The apparatus may further comprise a frequency converter coupled to the sequence changer to convert the modified preamble sequence into frequency tones. The apparatus may further comprise a tone mapper coupled to the frequency converter for mapping the frequency converter output to subcarriers. The apparatus may further comprise a frequency inverse transformer coupled to the tone mapper to convert the output of the tone mapper. The apparatus may further comprise a block repeater coupled to the frequency inverse transformer to repeat the output of the frequency inverse transformer, and a block repeat selector coupled to the block repeater to select block repetition. The apparatus may further comprise a cyclic prefix inserter coupled to the block repeater to add a cyclic prefix to the block repeater output.

A second embodiment of the present invention disclosed includes a random access signal transmission apparatus including a CAZAC route sequence selector coupled to a CAZAC route sequence generator, wherein the CAZAC route sequence generator generates at least one CAZAC route sequence, and CAZAC The root sequence selector selects a preamble root sequence from at least one CAZAC root sequence. The apparatus may further comprise a tone mapper coupled to the CAZAC route generator to map the preamble route sequence to the subcarriers. The apparatus may further comprise a frequency inverse transformer coupled to the tone mapper to convert the output of the tone mapper. The apparatus may further comprise a sequence changer coupled to the frequency inverse transformer to change the frequency inverse transformer output, and a sequence change selector coupled to the sequence changer to select the sequence change. The sequence changer may also include a cyclic shifter. The apparatus may further include a block repeater coupled to the sequence changer to repeat the output of the sequence changer, and a block repeat selector coupled to the block repeater to select block repetition. The apparatus may further comprise a cyclic prefix inserter coupled to the block repeater to add a cyclic prefix to the block repeater output.

A third embodiment of the present invention disclosed includes a random access signal transmission apparatus including a CAZAC route sequence selector coupled to a CAZAC route sequence generator, wherein the CAZAC route sequence generator generates at least one CAZAC route sequence, and CAZAC The root sequence selector selects a preamble root sequence from at least one CAZAC root sequence. The apparatus may further comprise a frequency converter coupled to the sequence changer to convert the modified preamble sequence into frequency tones. The apparatus may further comprise a tone mapper coupled to the CAZAC root sequence generator to map the preamble root sequence to the subcarriers. The apparatus may further comprise a frequency inverse transformer coupled to the tone mapper, for converting the output of the tone mapper. The apparatus may further comprise a sequence changer coupled to the frequency inverse transformer to change the output of the frequency inverse transformer, and a sequence change selector coupled to the sequence changer to select a sequence change. The sequence changer may also be a cyclic shifter. The apparatus may further comprise a block repeater coupled to the sequence modifier to repeat the output of the sequence changer, and a block repeat selector coupled to the block repeater to select block repeats. The apparatus may further comprise a cyclic prefix inserter coupled to the block repeater to add a cyclic prefix to the output of the block repeater.

In another aspect, an embodiment of the present disclosure includes a random access signal receiving apparatus including a frequency converter coupled to a complex multiplier to convert a root CAZAC sequence into pilot tones. The apparatus may further comprise a subcarrier demapping component coupled to the complex multiplier to demap subcarrier mapped frequency tones. The apparatus may further comprise a frequency converter coupled to the subcarrier demapper to convert the random access signal into subcarrier mapped frequency tones. The apparatus may further comprise a cyclic prefix remover coupled to the frequency converter to remove the cyclic prefix from the random access signal. The apparatus may further comprise a frequency inverse transformer coupled to the complex multiplier to convert the complex multiplier output into a time signal. The apparatus may further comprise an energy detector coupled to the frequency inverse transformer to detect a peak correlation between the random access signal and the root CAZAC sequence.

A first method of the disclosed invention is a method of accessing a wireless network, comprising transmitting a signal, the signal comprising a CAZAC sequence selected from a plurality of CAZAC sequences. The method may further comprise a fraction length zadoff-Chu sequence. In addition, the duration of the signal is determined independently for each network cell. Integer number of resource blocks are allocated for transmission of the signal, and the duration of the signal is an integer number of data symbols. The plurality of CAZAC sequences are subdivided into groups including non-competitive use groups and competitive use groups. The plurality of CAZAC sequences includes CAZAC sequences generated by applying changes to at least one root CAZAC sequence. Changes applied to the at least one root CAZAC sequence include cyclic shifts. The cyclic shifts applied to the at least one root CAZAC sequence are integer multiples of (maximum cell round trip delay + delay spread) of the communication network cell. The method may further comprise determining cyclic shifts applied to the at least one root CAZAC sequence, independently for each communication network cell. The method may further include analyzing the signal to estimate a frequency response of an uplink transmission channel, and assigning uplink resources based on the frequency response estimate. The method may further include analyzing the random access preamble signal to estimate the uplink frequency response. The method may further include allocating uplink resources based on the estimated uplink frequency response. The method may further comprise transmitting at least one wideband pilot signal. The method may further comprise analyzing the wideband pilot signal to estimate the frequency response of the uplink. The method may further include a method of assigning uplink resources based on the estimated uplink frequency response. The plurality of CAZAC sequences represent a plurality of information values. The information represented by the random access preamble signal includes at least one of a downlink channel quality indicator and a random access cause. The method may further include allocating transmission resources according to the random access cause. The method may further comprise balancing communication network cell load by selective access restriction according to the random access cause. The method may further comprise subdividing the plurality of CAZAC sequences into access type groups. The method may further comprise assigning the plurality of CAZAC sequences to access type groups in accordance with latency requests of the access type. The method may further comprise randomly selecting a CAZAC sequence to be transmitted from the plurality of CAZAC sequences assigned to the access type. The method may further comprise subdividing the plurality of CAZAC sequences assigned to each access type into subgroups, each representing an information value. The method may further comprise determining, for each communication network cell, the number of CAZAC sequences per access type group, and the granularity of the access type groups into information representation subgroups.

A second method of the present invention disclosed is a method for adapting a random access preamble for uplink transmission, comprising: calculating a frequency domain CAZAC sequence; Storing the frequency domain CAZAC sequence in a storage device; Reading a frequency domain CAZAC sequence from the storage device; And mapping the frequency domain CAZAC sequence to subcarriers assigned to the random access channel.

Also disclosed is a method of resolving random access signal collisions, the method comprising randomly selecting one random access preamble signal from a plurality of random access preamble signals; And delaying transmission of the random access signal.

While embodiments of the invention have been shown and described, changes may be made by those skilled in the art without departing from the spirit or teachings of the invention. The embodiments described herein are illustrative, not limiting. Various modifications and variations of the system and apparatus are possible and are within the scope of the present invention. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, and the scope shall include all equivalents of the content of the claims.

Claims (29)

An apparatus for transmitting a random access signal, CAZAC root sequence selector combined with CAZAC root sequence generator Including, The CAZAC root sequence generator generates at least one CAZAC root sequence, And the CAZAC root sequence selector autonomously selects a preamble root sequence from the at least one CAZAC root sequence. The apparatus of claim 1, wherein the CAZAC root sequence generator is a Zadoff-Chu sequence generator. The method of claim 1, A sequence changer coupled to the CAZAC root sequence generator to change the preamble root sequence, and A sequence change selector coupled to the sequence changer to select a preamble root sequence change Device further comprising. 4. The apparatus of claim 3, wherein the sequence changer comprises a cyclic shifter. 4. The apparatus of claim 3, further comprising a frequency converter coupled to the sequence changer to convert a modified preamble sequence into frequency tones. 6. The apparatus of claim 5, further comprising a tone mapper coupled to the frequency converter to map frequency converter output to subcarriers. 7. The apparatus of claim 6, further comprising a frequency inverse transformer coupled to the tone mapper to transform the output of the tone mapper. The method of claim 7, wherein A block repeater coupled to the frequency inverse transformer and repeating the output of the frequency inverse transformer, A block repeat selector coupled to the block repeater to select block repeats, and A cyclic prefix inserter coupled to the block repeater, for adding a cyclic prefix to the block repeater output Device further comprising. 2. The apparatus of claim 1, further comprising a tone mapper coupled to the CAZAC root sequence generator to map a preamble root sequence to subcarriers. 10. The apparatus of claim 9, further comprising a frequency inverse transformer coupled to the tone mapper to transform the output of the tone mapper. The method of claim 10, A sequence changer coupled to the frequency inverse transformer, for altering the frequency inverse transformer output, and A sequence change selector coupled to the sequence changer to select a sequence change Device further comprising. 12. The apparatus of claim 11, wherein the sequence changer comprises a cyclic shifter. The method of claim 12, A block repeater coupled to the sequence changer, for repeating the output of the sequence changer, A block repeat selector coupled to the block repeater to select block repeats, and A cyclic prefix inserter coupled to the block repeater, for adding a cyclic prefix to the block repeater output Device further comprising. The method of claim 1, A frequency converter coupled to the CAZAC root sequence generator to convert a preamble root sequence into frequency tones, A tone mapper, coupled to the frequency converter, to map frequency converter output to subcarriers; A frequency inverse transformer coupled to the tone mapper to convert the output of the tone mapper Device further comprising. The method of claim 14, A sequence changer coupled to the frequency inverse transformer, for changing an output of the frequency inverse transformer, and A sequence change selector coupled to the sequence changer to select a sequence change Device further comprising. 16. The apparatus of claim 15, wherein the sequence changer comprises a cyclic shifter. The method of claim 16, A block repeater coupled to the sequence changer, for repeating the output of the sequence changer, A block repeat selector coupled to the block repeater to select block repeats, and A cyclic prefix inserter, coupled to the block repeater, to add a cyclic prefix to the output of the block repeater Device further comprising. As a method of accessing a wireless network, Transmitting the signal Including, The signal comprises a CAZAC sequence autonomously selected from a plurality of CAZAC sequences. 19. The method of claim 18, wherein the CAZAC sequence further comprises a Zadoff-Chu sequence. 19. The method of claim 18, wherein the duration of the signal is determined independently for each network cell. The method of claim 18, Integer number of resource blocks are allocated for transmission of the signal, The signal duration is an integer number of data symbols. 19. The method of claim 18, wherein the plurality of CAZAC sequences is subdivided into groups comprising a non-competitive use group and a competitive use group. 19. The method of claim 18, wherein the plurality of CAZAC sequences comprises CAZAC sequences generated by applying changes to at least one root CAZAC sequence. 24. The method of claim 23, wherein the changes applied to the at least one root CAZAC sequence include cyclic shifts. 25. The method of claim 24, wherein the cyclic shifts applied to the at least one root CAZAC sequence are government multiples of (maximum cell round trip delay + delay spread) of a communication network cell. 25. The method of claim 24, further comprising independently determining, per communication network cell, cyclic shifts applied to the at least one root CAZAC sequence. 19. The method of claim 18, further comprising transmitting at least one wideband pilot signal. 19. The method of claim 18, wherein the plurality of CAZAC sequences represent a plurality of information values. A method of allocating uplink resources, Receiving a signal comprising at least one of a selected CAZAC sequence and a wideband pilot signal from the plurality of CAZAC sequences; Analyzing the signal to estimate a frequency response of an uplink transmission channel; And Allocating uplink resources based on the frequency response estimate How to include.

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