JP2019075806A - Simple RACH (SRACH) - Google Patents

Abstract

To provide systems and methods for providing random access in a cellular communications network.SOLUTION: Random access is performed using a physical random access channel (PRACH) including subcarriers having a subcarrier frequency spacing that is equal to a subcarrier frequency spacing in one or more other channels of an uplink (e.g., a physical uplink shared channel (PUSCH)). As a result, the subcarriers in the PRACH are orthogonal to the subcarriers in the other channels of the uplink, which in turn reduces, or substantially eliminates, interference between the PRACH subcarriers and the subcarriers of the other channels of the uplink.SELECTED DRAWING: Figure 8

Description

  The present disclosure relates to random access in cellular communication networks.

Random access is a basic component of any cellular communication network. In general, random access enables wireless devices, referred to as user equipment (UE) in the 3 ^rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard, to request connection setup. Random access is diverse, including establishing the radio link upon initial access to the cellular communication network, reestablishing the radio link after radio link failure, establishing uplink synchronization for new cells for handover, etc. It can be used for the purpose. As shown in FIG. 1, in 3GPP LTE, a random access procedure is performed after first performing a cell search procedure. More specifically, the extension node B (eNB) 10 broadcasts primary and secondary synchronization signals (PSS / SSS) and system information (step 1000). The UE 12 performs a cell search procedure whereby the UE 12 detects the PSS / SSS and synchronizes to the downlink timing of the cell served by the eNB 10 (step 1002). Then, the UE 12 acquires or reads system information (step 1004). The system information includes various types of information including information identifying physical time and frequency resources to be used by the UE 12 for random access.

  Regarding the random access procedure, the UE 12 sends a random access preamble (step 1006). The random access preamble is transmitted on a random access channel (RACH), which is a logical transport channel. The RACH is mapped to a physical RACH (PRACH), and the PRACH is provided on time and frequency radio resources indicated by system information broadcasted by the eNB 10. The eNB 10 detects the random access preamble transmitted by the UE 12 and determines the uplink timing for the UE 12 based on the random access sequence transmitted there (step 1008). Then, the eNB 10 transmits a random access response including a timing adjustment value for uplink from the UE 12 to the UE 12 (Step 1010). The UE 12 adjusts its uplink timing according to the timing adjustment value received in the random access response (step 1012). Then, the UE 12 and the eNB 10 exchange information for completing establishment of a radio link between the eNB 10 and the UE 12 using radio resource control (RRC) signaling (steps 1014 and 1016).

As shown in FIG. 2, the random access preamble, also referred to herein as the RACH preamble, includes a sequence having a time length T _SEQ (herein referred to as a RACH sequence) and a cyclic prefix (CP) having a time length T _CP. Including. The CP is added to the RACH sequence in order to reduce inter-symbol interference (ISI). The RACH sequence is a Zadoff-Chu (ZC) sequence of N _ZC points, where N _ZC = 839. N _ZC is the length of the ZC sequence and hence the length of the RACH sequence. In 3GPP LTE, cell sizes up to about 150 kilometers (km) (radius) are supported. In order to provide this support, the length of time (T _SEQ ) of the RACH sequence must be significantly larger than the round trip time for the largest supported cell size. Specifically, 3GPP LTE defines four random access configurations (configurations 0 to 3). For each configuration, the RACH sequence spans one or more 0.8 millisecond (ms) (transmission) cycles. A typical random access configuration is configuration 0. In configuration 0, the RACH sequence is a 0.8 ms sequence, so that the RACH sequence spans only one 0.8 ms cycle. In particular, in configuration 0, T _SEQ = 0.8 ms, T _CP = 0.1 ms, and the guard time (not shown) is also equal to 0.1 ms. Configuration 0 allows cell sizes (radius) up to 15 km. In order to support larger cell sizes (ie up to 150 km), configurations 1 to 3 use longer CPs and in the case of configurations 2 and 3 the sequence length is longer (ie T _SEQ = 1.6 ms) span multiple subframes. For example, in configuration 2, T _SEQ = 1.6 ms, T _CP = 0.2 ms, and the guard time (not shown) is also equal to 0.2 ms. In configuration 2, the RACH sequence (time length T _SEQ = 1.6 ms) spans two 0.8 ms cycles. However, each cycle has a length of 0.8 ms and corresponds to a subcarrier frequency interval (Δf _PRACH ) for a 1.25 kHz PRACH subcarrier (ie, Δf _PRACH = 1 / T _CYC = 1 / 0.8 ms = 1.25 kHz, where T _{CYC is referred} to as cycle time).

The PRACH used to transmit the RACH preamble is six resource blocks (RBs) in the frequency domain. In the time domain, the PRACH is one subframe (1 ms) (configuration 0), 2 subframes (2 ms) (configuration 1 or 2), or 3 subframes (3 ms) (configuration 3) . FIG. 3 shows the PRACH for configuration 0. As shown, in order to fit a 0.8 ms sequence to 6 RBs in the frequency domain and to provide orthogonality between PRACH subcarriers, the subcarrier frequency interval (Δf _PRACH ) for PRACH subcarriers is 1.25 Kilohertz (kHz) (ie, Δf _PRACH = 1 / T _CYC = 1 / 0.8 ms = 1.25 kHz). Thus, as illustrated, the subcarrier frequency interval (Δf _PRACH ) for PRACH subcarriers is the subcarrier frequency for the subcarriers of other uplink channels (eg, physical uplink shared channel (PUSCH)), which is 15 kHz. It is 1/12 of the interval (Δf _TRAFFIC ). For PRACH, there are 864 PRACH subcarrier allocations in the range of 6 RBs. Among these 864 PRACH subcarriers, 839 PRACH subcarriers are used for transmission of the 839-point ZC sequence.

One issue with the 3GPP LTE legacy PRACH is that the processing of the PRACH at both the transmitter and receiver is complicated due to the large number of PRACH subcarriers. Specifically, FIG. 4 shows a legacy PRACH preamble transmitter 14. As shown, RACH sequence for the RACH preamble (in the time domain), a discrete Fourier transform (DFT) (e.g., fast Fourier transform (FFT)) is input to function 16, DFT function _{16, N ZC} point Perform an FFT of Again, N _ZC = 839 for 3GPP LTE. The RACH sequence is a ZC sequence of 839 points. The cycle time or length of time (T _CYC ) of the RACH sequence is 0.8 ms, so the frequency spacing of the frequency bins at the output of the FFT function 16 is 1 / T _CYC = 1.25 kHz. Subcarrier mapping function 18 maps the output of FFT function 16 to the appropriate PRACH subcarrier of the uplink system bandwidth.

The output of the subcarrier mapping function 18 is provided to the corresponding input of an Inverse Discrete Fourier Transform (IDFT) (eg, Inverse FFT (IFFT)) function 20. The size of IFFT 20 (herein referred to as N _DFT ) is T _CYC · f _s where f _s is the sampling rate. For a system bandwidth of 20 megahertz (MHz), 3GPP LTE uses a sampling rate of 30.72 MHz, so the size of IFFT 20 is 24,576. (Ie, N _DFT = T _CYC · f _s = 800 microseconds (μs) · 30.72 MHz). The large size of the IFFT 20 results in a significant amount of resources and complexity in implementing the RACH preamble transmitter 14. The iteration function 22 repeats the time domain sequence output by the IFFT 20 as needed according to the random access configuration. Finally, the CP insertion function 24 inserts a CP, whereby the final time domain RACH preamble is output for transmission.

  In the same way, small RACH subcarrier spacing results in complexity in legacy RACH preamble receivers. As shown in FIG. 5, legacy device 26 typically includes traffic path 28 and RACH path 30, where RACH path 30 is a legacy RACH preamble receiver. The normal traffic path 28 includes a data processing unit 32. The data processing unit 32 includes a CP removal function 34, a frequency shift function 36, and a symbol FFT function 38. The CP removal function 34 removes the CP of the received signal. The frequency shift function 36 then shifts the frequency of the received signal by one half of the normal subcarrier spacing (ie, 15/2 kHz = 7.5 kHz). The received signal is then divided into time fragments corresponding to fractions of a millisecond (e.g. 1/14 or 1/12), referred to as symbols. The symbol FFT function 38 then performs an FFT for each symbol. Specifically, for a 20 MHz bandwidth, symbol FFT function 38 performs a 2,048 point FFT for each symbol. The resulting frequency domain signal fragments are then provided to uplink processing function 40 for further signal processing.

  For the RACH path 30, the "super FFT" function 42 performs a 0.8 ms FFT of the samples of the received signal. For a 20 MHz bandwidth, the size of the FFT is 24,576. Thus, due to the large size of the FFT, the FFT is referred to herein as a "super-FFT". The super-FFT function 42 involves a large amount of data and buffers to be transported and requires a large amount of computation. The output of super-FFT function 42 is then provided to data processor 44. The data processing unit 44 includes an RACH subcarrier selection function 46, a correlation function 48, and an IFFT function 50. The RACH subcarrier selection function 46 selects 839 outputs of the super FFT function 42 corresponding to the RACH subcarrier. The correlation function 48 then performs a correlation operation between the output of the RACH subcarrier selection function 46 and the known ZC sequence, thereby extracting the temporary identifier of the UE being transmitted. More specifically, the correlation function 48 multiplies the received RACH subcarrier with the conjugate of one of the known ZC sequences in the frequency domain. This efficiently and simultaneously correlates all the time shifts of the ZC sequence in one step. The IFFT function 50 then performs 2,048 points of IFFT to produce a time domain signal, which is then processed by the RACH detection module 52. The output of the IFFT function 50 indicates where some correlation peak is located in time. Among other things, correlation (in the frequency domain) and IFFT are performed once for each of the desired ZC sequences. While the super FFT function 42 is a considerable burden in terms of storage space and power, most of the output of the super FFT function 42 is discarded in the data processing unit 44.

  U.S. Pat. No. 8,634,288 (B2), filed Jun. 1, 2011 and entitled "SYMBOL FFT RACH PROCESSING METHODS AND DEVICES", issued on Jan. 21, 2014, has a super FFT. Systems and methods for extracting RACH preambles without use are described. One embodiment of the device 54 disclosed in US Pat. No. 8,634,288 B2 is shown in FIG. As shown, the apparatus 54 includes a device 56 for extracting the RACH preamble from the received signal in a manner that eliminates the need for super-FFT. Specifically, device 54 includes traffic paths and RACH paths. The traffic path is the same as that of FIG. On the other hand, the RACH path includes a data processor 32 (also used for the traffic path), a device 56, a data processor 44 for the RACH path, and an RACH detection module 52. Unlike the legacy device 26 of FIG. 4, the device 54 of FIG. 5 uses the data processing portion 32 of the traffic path as part of the RACH path with the device 56 for eliminating the super-FFT function 42. As a result, the complexity is substantially reduced.

  Specifically, for the RACH path, the output of the symbol FFT function 38 for a predetermined number of symbols (eg, 12) is input to the device 56 one by one. Within device 56, demapping function 58 selects the portion of the signal where the RACH should be located. Due to the coarser FFT (ie, the FFT performed by the symbol FFT function 38), the selected portion of the signal covers about 72 discrete frequencies in the output spectrum of the symbol FFT over about 1 MHz. Do. The selected portion of the signal (all other non-RACH frequency bins are set to zero) is shifted to baseband.

  The IFFT function 60 performs a 256 point IFFT on selected portions of the signal, thereby reconverting the selected portions of the signal into the time domain. The phase adjustment function 62 performs phase adjustment to compensate for the collective delay of the symbol CP gap when moving the data to the baseband (the phase of the first sample of the IFFT output is the last signal of CP time) (Not necessarily equal to the phase of, and may be zero or some other value). The CP zero insertion function 64 inserts a zero into the symbol CP time and the downsampling function 66 downsamples the signal by a factor of three. Downsampling occurs to limit the number of points in the sequence corresponding to the RACH preamble to the required and relevant number of points (the number of 256 points used in IFFT function 60 is more than 3.72 This is the number of frequencies corresponding to the RACH band after demapping, which number is further increased by the insertion of the symbol CP). Data processing in functions 58-66 is performed for each of the considered symbols (e.g., the number of symbols may be twelve).

  The output of the downsampling function 66 is accumulated by the accumulation function 66, and then the RACH preamble part is selected by the preamble selection function 70. The FFT function 72 then performs a 1,024 point FFT. The frequency interval of the output bins of the FFT function 72 is 1.25 kHz, and 839 of the output bins of the FFT function 72 correspond to 839 PRACH subcarriers. The output of FFT function 72 is then input to data processor 44 and processing continues in the manner discussed above. In this way, by using device 56, the output of symbol FFT function 38 can be used for RACH extraction. However, since the frequency interval of the output of the symbol FFT function 38 is 15 kHz, the device 56 recovers PRACH subcarriers having a subcarrier interval of 1.25 kHz from the output of the symbol FFT function 38 having an interval of 15 kHz. To work.

  The system and method of US Pat. No. 8,634,288 (B2) provides substantial benefits in terms of complexity reduction. However, in both the legacy RACH receiver used in device 26 of FIG. 5 and the RACH receiver implemented in device 54 of FIG. 6, normal traffic (eg, PUSCH traffic) interferes during RACH detection. And vice versa. Thus, there is a need for systems and methods that reduce or eliminate interference between RACH transmissions and normal traffic transmissions.

  Disclosed are systems and methods for random access in a cellular communication network. In general, the cellular communication network may be an Orthogonal Frequency Division Multiplexing (OFDM) based cellular communication network (eg, 3rd Generation Partnership Program (3GPP) Long Term Evolution (LTE) cellular communication network) or similar multi-subcarrier based cellular communication network It is. However, in one embodiment, the cellular communication network is a 3GPP LTE cellular communication network or some derivative thereof. Random access is a physical random access channel (including multiple subcarriers with subcarrier frequency spacing equal to the subcarrier frequency spacing in one or more other channels of the uplink (eg, physical uplink shared channel (PUSCH)) It is performed using PRACH). As a result, the subcarriers in PRACH become orthogonal to the subcarriers in the other channel of uplink, which in turn reduces the interference between the PRACH subcarriers and the subcarriers of the other channel of uplink. Or substantially eliminate it.

  In one embodiment, a method of operating a wireless device is provided to perform random access in a cellular communication network. In one embodiment, the method includes transmitting a RACH preamble on the PRACH on the uplink, from the wireless device to a radio access node in the cellular communication network. The PRACH includes a plurality of subcarriers with subcarrier frequency spacing equal to the subcarrier frequency spacing of the uplink one or more other channels (eg, uplink PUSCH). The method further includes receiving a random access response from the radio access node in response to the transmission of the RACH preamble.

  In one embodiment, the cellular communication network is an OFDM based cellular communication network. In one specific embodiment, the cellular communication network is an LTE cellular communication network.

  In one embodiment, the subcarrier frequency spacing of both the plurality of subcarriers in the PRACH and the subcarriers in the one or more other channels of the uplink is 15 kilohertz (kHz). In another embodiment, the subcarrier frequency spacing of both the plurality of subcarriers in the PRACH and the subcarriers in the one or more other channels of the uplink is X · 15 kHz, where X> 1.

  In one embodiment, transmitting the RACH preamble generates a basic RACH sequence for one transmission cycle of the RACH sequence of the RACH preamble, and converts the basic RACH sequence from time domain to frequency domain Providing a frequency domain representation of the basic RACH sequence, and mapping the frequency domain representation of the basic RACH sequence to an appropriate frequency offset for the PRACH within the uplink system bandwidth Providing a mapped frequency domain representation of the basic RACH sequence, and transforming the mapped frequency domain representation of the basic RACH sequence from the frequency domain to the time domain. By comprises, providing a sample of the RACH sequence for the RACH preamble for one symbol period of the PRACH. The length of the basic RACH sequence has a length equal to or less than the number of subcarriers in the PRACH. In one embodiment, the samples generated from the basic RACH sequence are repeated Q times a total of Q times to provide the RACH sequence, where Q is one or more.

  In one embodiment, transmitting the RACH preamble repeats the samples for the RACH sequence of the RACH preamble by one or more additional transmission cycles for the RACH sequence of the RACH preamble. And further include.

  In another embodiment, the number of samples (Z) of the RACH sequence for the RACH preamble provided for one transmission cycle depends on the time length of the basic RACH sequence and the system bandwidth of the uplink. It is defined as a product of a system sample rate and transmitting the RACH preamble means that the Z samples of the RACH sequence of the RACH preamble are Q samples of 2 or more, and the Q samples of the RACH sequence of the RACH preamble are The method further includes: repeating the transmission cycle of

  In another embodiment, transmitting the RACH preamble comprises: transmitting, for the one transmission cycle of the RACH sequence of the RACH preamble, a number of ciclips preambles at the beginning of the samples of the RACH sequence of the RACH preamble. Inserting a fix (CP) sample, repeating the sample for the RACH sequence of the RACH preamble for the second transmission cycle of the RACH sequence of the RACH preamble, and the RACH for the transmission cycle Inserting a certain number of CP samples at the beginning of the samples of the RACH sequence of the preamble. The CP samples are not part of the RACH CP and are generated in a process equivalent to that done in the case of PUSCH symbols so that the CP samples actually form part of the RACH sequence of the RACH preamble Be done.

  In one embodiment, the method comprises, during transmission of the RACH preamble, receiving from the radio access node a request for an early stop of transmission of the RACH preamble, and in response to receiving the request. Stopping transmission of the preamble.

  In one embodiment, the bandwidth of the PRACH is 1.08 megahertz (MHz), both the plurality of subcarriers in the PRACH and the subcarriers in the one or more other channels of the uplink. The subcarrier frequency interval of is 15 kHz, and the length of the basic RACH sequence is 72 or less. In one embodiment, the basic RACH sequence is a Zadoff-Chu (ZC) sequence, and the length of the basic RACH sequence is 71.

  In another embodiment, the bandwidth of the PRACH is X · 1.08 MHz, and the subcarriers of both the plurality of subcarriers in the PRACH and the subcarriers in the one or more other channels of the uplink. The frequency interval is X · 15 kHz as X> 1, and the length of the RACH sequence is 72 or less. In one embodiment, the RACH sequence is a ZC sequence, and the length of the RACH sequence is 71.

  In another embodiment, the bandwidth of the PRACH is X.M.15 kHz, and the subcarriers of both the plurality of subcarriers in the PRACH and the subcarriers in the one or more other channels of the uplink. The frequency interval is X · 15 kHz, where X> 1, and the length of the RACH sequence is M or less. The RACH sequence is a ZC sequence, and the length of the RACH sequence is the largest prime number of M or less.

  In another embodiment, a wireless device configured to operate in accordance with any one of the above-described embodiments is disclosed.

  Those skilled in the art will recognize the scope of the present disclosure and understand those additional aspects after reading the following detailed description of the embodiments in connection with the accompanying drawing figures.

  The drawings in the accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

Fig. 3 illustrates a legacy cell search and random access procedure in 3 rd Generation Partnership Program (3 GPP) Long Term Evolution (LTE) network. Fig. 2 illustrates a legacy random access channel (RACH) preamble. Figure 10 illustrates subcarrier frequency intervals for a legacy physical random access channel (PRACH) relative to subcarrier frequency intervals of other uplink traffic channels. Fig. 2 shows a legacy RACH preamble transmitter. FIG. 1 shows an apparatus including a normal uplink traffic processing path and a legacy RACH preamble receiver. FIG. 1 shows an apparatus including a normal uplink traffic processing path and a reduced complexity RACH preamble receiver. 1 illustrates a cellular communication network that utilizes a Simple Random Access Channel (SRACH) according to one embodiment of the present disclosure. 8 illustrates subcarrier frequency intervals for one example of a simple physical random access channel (SPRACH) relative to subcarrier frequency intervals of another uplink traffic channel, according to one embodiment of the present disclosure. Fig. 2 shows one slot of an uplink subframe for a cellular communication network of scaled frequency. 8 illustrates subcarrier frequency spacing for one example of a SPRACH relative to subcarrier frequency spacing of another uplink traffic channel in a frequency scaled cellular communication network, in accordance with one embodiment of the present disclosure. 7 illustrates a cell search and random access procedure utilizing a SRACH preamble transmitted on a SPRACH in accordance with one embodiment of the present disclosure. 7 illustrates a process for generating a SRACH preamble in accordance with one embodiment of the present disclosure. FIG. 10 is a block diagram of the wireless device of FIG. 7 operative to generate a SRACH preamble in accordance with the process of FIG. 12 in accordance with one embodiment of the present disclosure. FIG. 8 is a block diagram of the base station of FIG. 7 operative to detect SRACH preambles generated and transmitted by a wireless device in accordance with an embodiment of the present disclosure; FIG. 10 illustrates an early stop process for stopping transmission of SRACH preambles according to an embodiment of the present disclosure. FIG. 10 shows a process for generating a SRACH preamble according to another embodiment of the present disclosure. FIG. 8 is a block diagram of the base station of FIG. 7 according to one embodiment of the present disclosure. FIG. 8 is a block diagram of the wireless device of FIG. 7 in accordance with an embodiment of the present disclosure.

  The embodiments described below represent the information that enables one of ordinary skill in the art to practice the embodiments and exemplify the best aspects of the practice of the embodiments. Those skilled in the art will understand the concepts of the present disclosure and will appreciate the application of those concepts not specifically set forth herein upon reading the following description in view of the accompanying drawings. It is to be understood that the concepts and applications fall within the scope of the present disclosure and the appended claims.

  Disclosed are systems and methods for random access in a cellular communication network. In general, the cellular communication network may be an Orthogonal Frequency Division Multiplexing (OFDM) based cellular communication network (eg, 3rd Generation Partnership Program (3GPP) Long Term Evolution (LTE) cellular communication network) or similar multi-subcarrier based cellular communication network It is. Random access is a physical random access channel (including multiple subcarriers with subcarrier frequency spacing equal to the subcarrier frequency spacing in one or more other channels of the uplink (eg, physical uplink shared channel (PUSCH)) It is performed using PRACH). As a result, the subcarriers in PRACH become orthogonal to the subcarriers in the other channel of uplink, which in turn reduces the interference between the PRACH subcarriers and the subcarriers of the other channel of uplink. Or substantially eliminate it. Note that the term uplink channel includes uplink signals (eg, demodulation reference signal (DRS) or sounding reference signal (SRS)). The equality of the RACH subcarrier spacing may be as it is for the uplink signal, but for the sake of brevity and clarity the term channel will be used here.

  In this regard, FIG. 7 shows one example of a cellular communication network 74 that utilizes PRACH for random access in accordance with one embodiment of the present disclosure. In particular, for the purpose of distinguishing the PRACH and the Random Access Channel (RACH) disclosed herein from the old PRACH and the old RACH, the PRACH and RACH disclosed herein are simple PRACH (SPRACH) in most of the following discussion. And referred to as simple RACH (SRACH). This is done solely for the simplicity and ease of the discussion. The term "simple" should be interpreted to mean something beyond the fact that the subcarrier spacing used for the SPRACH / SRACH disclosed herein is equal to the subcarrier spacing of other uplink channels is not.

  In the embodiment described herein, the cellular communication network 74 is preferably some future generation of a 4th generation (4G), a 5th generation (5G), or a 3GPP LTE cellular communication network. Therefore, 3GPP LTE terminology is often used here. However, it should be understood that the systems and methods disclosed herein are not limited to 3GPP LTE. Rather, the systems and methods disclosed herein may be used in any OFDM based cellular communication network or any multiple subcarrier based cellular communication network (eg, not limited to OFDM).

  As illustrated, the cellular communication network 74 includes a base station 76 serving a cell 78 and a wireless device 80, wherein the wireless device 80 is referred to as a user equipment (UE) in 3GPP LTE. Base station 76 may be a macro base station or a high power base station, and is referred to as an enhanced node B (eNB) in 3GPP LTE. Base station 76 may alternatively be a low power base station (eg, micro, pico, femto or home eNB). It should be noted that although the base station 76 is used in the embodiments described below, they are equally applicable to any radio access node that handles transmission of random access preambles.

The wireless device 80 is served by, for example, establishment of a radio link upon initial access to the cellular communication network 74, reestablishment of a radio link with the base station 76 after radio link failure, base station 76 for handover. Perform random access for various purposes, including establishing uplink synchronization with cell 78, and so on. During a random access period, the wireless device 80 transmits the SRRACH preamble on the SPRACH. The legacy RACH preamble has a 0.8 millisecond (ms) cycle to support large cell sizes (ie, greater than 15 km (km) and up to about 150 km radius) in older 3GPP LTE networks. It contains a Zadoff-Chu (ZC) sequence transmitted one or more times (ie, T _CYC = 0.8 ms). The length of the ZC sequence for one cycle is referred to as N _ZC . For the most common RACH configuration (configuration 0), the RACH preamble contains the ZC sequence of N _ZC points transmitted on one cycle, N _ZC equals 839 (ie, the ZC sequence is 839 in length), The time length of the ZC sequence is 0.8 ms (ie, the time length is equal to T _CYC = 0.8 ms). The subcarrier frequency interval in the legacy PRACH is 1.25 kilohertz (kHz), in order to maintain orthogonality between multiple subcarriers in the legacy PRACH, referred to herein as a PRACH subcarrier. , 1 / T _CYC = 1 / 0.8 ms = 1.25 kHz). However, while the 1.25 kHz subcarrier frequency spacing maintains orthogonality between the legacy PRACH subcarriers, this 1.25 kHz subcarrier frequency spacing of the PRACH is for other channels of the uplink (eg, PUSCH) And the subcarrier spacing of 15 kHz. Thus, legacy PRACH subcarriers are not orthogonal to subcarriers (eg, PUSCH subcarriers) for other uplink channels. As a result, legacy PRACH transmissions from one wireless device cause interference to, for example, PUSCH transmissions from other wireless devices, and vice versa.

In contrast, the SPRACH uses subcarrier spacing (Δf _SPRACH ), which is equal to the subcarrier spacing (Δf _TRAFFIC ) of one or more other channels (eg, PUSCH) on the uplink. The one or more other channels on the uplink may be referred to herein as normal traffic channels. Using 3GPP LTE as an example, Δf _SPRACH = Δf _TRAFFIC = 15 kHz. By using the same subcarrier frequency spacing for both the SPRACH and the other uplink channels, the SPRACH subcarriers become orthogonal to the subcarriers of the other channel (eg PUSCH) on the uplink, which in turn Interference between the SRACH preamble transmission and the uplink traffic transmission is substantially eliminated if not completely eliminated.

Similar to the legacy RACH preamble, the SRHACH preamble includes a cyclic prefix (CP) having a time length T _CP and a sequence (eg, a ZC sequence) having a time length T _SEQ . The sequence for the SRACH preamble is referred to herein as the SRACH sequence. The SRACH sequence comprises one or more repetitions of the same SRACH sequence, referred to herein as the basic SRACH sequence. 3GPP LTE legacy RACH preamble with cycle time or length (eg, 0.8 ms for 3GPP LTE) much longer than one normal traffic symbol time (eg, 66.7 microseconds (μs) for 3GPP LTE) Unlike, the SRACH preamble has a cycle time or length of time (T _CYC ) equal to one normal traffic symbol time. Thus, using 3GPP LTE as an example, SRACH has a cycle time (T _CYC ) equal to 1/15 kHz = 66.7 μs. In other words, the basic SRACH sequence has a length of time equal to T _CYC , which itself is equal to the normal traffic symbol time.

  In one embodiment, the SRACH preamble includes one instance of the SRACH cycle in the time domain and some defined number of resource blocks (RBs) (eg, 6 RBs in 3GPP LTE) in the frequency domain. In other embodiments, the SRACH preamble may include multiple repetitions of SRACH cycles and may span multiple subframes (e.g., two or three subframes as in random access configurations 1 to 3 of 3GPP LTE). . The repetition allows transmission of multiple repetitions of the basic SRACH sequence, thereby improving the sensitivity and time discrimination upon reception at the base station 76.

  In particular, the short length of the SRRACH cycle compared to the legacy RACH cycle means that the size of the cell 78 is limited to a smaller size than that supported using the legacy RACH preamble. For example, reducing the length of the SRACH cycle to 66.7 μs in a 3GPP LTE network limits the size of cell 78 to 10 km. In particular, the unambiguous cell radius that can use the SRACH preamble is 0.5 · 300 · 66.7 / X meter as X = 1 for 3GPP LTE and X> 1 for the frequency scaling version of 3GPP LTE. 300 is the electromagnetic propagation velocity in meters per second, and a factor of 0.5 accounts for bi-directional transmission time. Therefore, the maximum cell size is 10 km if X = 1, for example, the maximum cell size is 1 km if X = 10. Smaller cell sizes are not seen as a challenge, especially for the new and future generations of LTE (and other types of cellular communication networks). New future generations of LTE are planning to use or use smaller cell sizes. For example, heterogeneous network deployments, which may include many small low power cells, may be used. Also, small cell sizes are particularly promising for future 5G networks that are expected to use high density deployments of small base stations to support high traffic loads (eg, in cities).

FIG. 8 is a frequency domain representation of SPRACH according to one embodiment of the present disclosure. This example is for 3GPP LTE. However, again, the present disclosure is not limited thereto. In this example, the subcarrier frequency interval (Δf _SPRACH ) of the SPRACH subcarrier is 15 kHz, which is equal to the subcarrier frequency interval (Δf _PUSCH ) of the PUSCH subcarrier. Furthermore, in this example, the SPRACH spans 6 RBs in the frequency domain where each RB includes 12 subcarriers. Thus, the SPRACH consists of 72 SPRACH subcarriers (i.e., 6 RBs-12 SPRACH subcarriers / RB = 72 SPRACH subcarriers) and spans a total bandwidth of 1.08 MHz (i.e., 72 SPRACH subcarriers-15 kHz / SPRACH subcarriers = 1.08 MHz). In this example, the basic SRACH sequence is a 71 point ZC sequence (ie, N _ZC = 71). However, it should be noted that other types of sequences may be used, as will be appreciated by those skilled in the art. Since a 71 point sequence is used instead of 72 points, one of the SPRACH subcarriers is unused.

Importantly, the embodiment of FIG. 8 is only an example. For example, future generations of 3GPP LTE networks or other OFDM based cellular networks may allocate more or less than 6 RBs to the SPRACH channel in the frequency domain. As another example, subcarrier frequency intervals other than 15 kHz may be used. Further, the SPRACH channel and SRACH preamble may be used in a frequency scaled cellular communication network (eg, a frequency scaled LTE network), where the frequency is multiplied by a scaling factor X (eg, SPRACH subcarrier spacing Is equal to 15 kHz x), time is divided by its scaling factor X (e.g., the length of the SRRACH cycle is equal to 66.7 [mu] s / X). For example, for a 20 gigahertz (GHz) carrier, the scaling factor X may be, for example, ten. This is illustrated in FIGS. 9 and 10, among which FIG. 9 shows one slot of the uplink frame structure in the frequency scaling network and FIG. 10 shows the SPRACH in the frequency scaling network. In particular, in one embodiment, the SPRACH in the frequency scaling network has a bandwidth of X · M · 15 kHz, where M is the number of SPRACH subcarriers (M> 1), X is a scaling factor (X> 1), and With a subcarrier frequency spacing of X · 15 kHz (equal to the subcarrier frequency spacing of the other channels of the link), and the length of the basic SRACH sequence is less than or equal to M. Note that M = 72 and X = 1 is an embodiment of SPRACH in a 3GPP LTE network. In one embodiment, the basic SRACH _sequence the _{N ZC} as being less largest prime number _M, a ZC sequence of _{N ZC} points.

  FIG. 11 illustrates a cell search and random access procedure for the cellular communication network 74 of FIG. 7 in accordance with one embodiment of the present disclosure. Note that although Figure 11 and some other figures show "steps", the term "steps" should be interpreted as requiring any specific order for the execution of the associated action. It should be noted that not. Indeed, the steps may be performed in any desired order, unless it is specified that a particular order is required and a particular order is required for operation. Furthermore, some of the steps may be performed simultaneously.

  As shown, base station 76 broadcasts primary and secondary synchronization signals (PSS / SSS) and system information (step 2000). The wireless device 80 performs a cell search procedure whereby the wireless device 80 detects the PSS / SSS and synchronizes to the downlink timing of the cell 78 (step 2002). The wireless device 80 then obtains or reads system information (step 2004). System information includes various types of information including information identifying physical time and frequency resources to be used by the wireless device 80 for random access. More specifically, the system information includes information identifying the resource to be used for SRACH preamble transmission (ie identifying the SPRACH).

  Then, the wireless device 80 transmits the SRRACH preamble (step 2006). The SRRACH preamble is transmitted on SRACH, which is a logical channel mapped to SPRACH. The base station 76 detects the SRACH preamble transmitted by the wireless device 80 and determines uplink timing for the wireless device 80 (step 2008). From this point on, the proceedings proceed in the old fashion. Specifically, the base station 76 transmits a random access response including the timing adjustment value for the uplink from the wireless device 80 to the wireless device 80 (step 2010). The wireless device 80 then adjusts its uplink timing according to the random access response (step 2012). Then, the wireless device 80 and the base station 76 exchange information for completing establishment of a wireless link between the base station 76 and the wireless device 80 using radio resource control (RRC) signaling (step 2014 and 2016).

FIG. 12 shows a process for generating a SRHACH preamble to be transmitted by the wireless device 80 in accordance with one embodiment of the present disclosure. This process is performed by the wireless device 80. First, a basic SRACH sequence is generated in the time domain (step 3000). However, it should be noted that the basic SRACH sequence may alternatively be generated in the frequency domain. In that case, step 3002 may be skipped. The basic SRACH sequence consists of N _ZC complex values of ZC sequences or other sequences with good cross-correlation, autocorrelation and frequency domain characteristics. Although not essential, in one alternative embodiment, the basic SRACH sequence is described in "Complex Spreading Sequences with a Wide Range of Correlation Properties" (Ian Oppermann et al., IEEE Transactions on Communications, Vol. 45, No. 3). , March 1997, pages 365-375), which is incorporated herein by reference for its teaching of sequences suitable for basic SRACH sequences. For interworking with the existing 3GPP LTE standard, the basic SRACH, in one embodiment, may be 6 RBs (ie, 72 SPRACH subcarriers) in the frequency domain, with 15 kHz subcarrier spacing. In this case, N _ZC (more generally, the number of complex values in the basic SRACH sequence in the time domain) is 71. In particular, in the case of a ZC sequence, it is preferable that the number of complex values in the sequence be a prime number.

Then, performing a discrete Fourier transform (DFT) (e.g., a fast Fourier transform (FFT)) on the basic SRACH sequence in the time domain converts the basic SRACH sequence in the time domain into a frequency domain representation of the basic SRACH sequence (Step 3002). The number of points in the FFT is preferably equal to the number of complex values in the basic SRACH sequence in the time domain. Thus, for example, if the basic SRACH sequence is a _ZC sequence of N _ZC points, then the number of points in the FFT is equal to N _ZC . The frequency spacing of the output frequency bins of the FFT is equal to 1 / T _CYC , where T _CYC is the length or length of one cycle of the basic SRACH sequence. Thus, T _CYC is equal to the symbol length for the other traffic channel on the uplink, so that the frequency spacing of the output frequency bins of the FFT (and hence also the SPRACH subcarrier frequency spacing) are the subcarriers of the other channel on the uplink. Equal to the frequency interval. In one embodiment, T _CYC = 66.7 μs and N _ZC = 71. Therefore, the FFT is a 71-point FFT, and the frequency spacing of the output frequency bins of the FFT is equal to 15 kHz (ie 1 / 0.0667 ms = 15 kHz), which matches the desired subcarrier frequency spacing for other 3GPP LTE channels Do.

  The output of the DPR, which is a SPRACH subcarrier, is then mapped to the appropriate frequency offset for the SPRACH in the uplink (step 3004). More specifically, there are L subcarriers for the uplink, where L depends on the uplink bandwidth. In the frequency scaling versions of 3GPP LTE and 3GPP LTE, L = 1200 BW / (20 X). The SPRACH subcarriers output by DFT are mapped to the appropriate set of subcarriers in the range of uplink L subcarriers (ie, the subcarrier group assigned to PRACH)

Importantly, the length of the basic SRACH sequence in the time domain (ie, cycle time T _CYC ) is the frequency interval between the output bins of the FFT, and thus the SPRACH subcarrier frequency interval is another channel on the uplink (eg, The PUSCH, physical uplink control channel (PUCCH), etc.) is selected to be equal to the subcarrier frequency spacing. Thus, the SPRACH subcarriers will be orthogonal to the other uplink channel subcarriers at base station 76. This orthogonality to the other uplink channel subcarriers reduces, if not eliminate, the need for a guard band at the outer edge of the SPRACH in the frequency domain. Such guard bands are required for the legacy 3GPP LTE PRACH. The exclusion of the guard band may be possible because there is no leakage between the data / control subcarriers and the SPRACH subcarriers. In addition, orthogonality of SPRACH subcarriers will result in improved signal to interference and noise ratio (SINR) as well as system performance.

After mapping, frequency domain samples are transformed into Z time domain samples by performing Z-point inverse discrete Fourier transform (IDFT) (eg Z-point inverse fast Fourier transform (IFFT) on the frequency domain samples Step 3006). The value of Z depends on the sampling rate. Specifically, _assuming that F _s is a sampling rate, Z = T _CYC · f _s . For example, in 3GPP LTE, the sampling rate when using a bandwidth of 20 MHz) MHz) is 30.72 megasamples per second (Msps). Thus, Z equals 2,048 if T _CYC = 66.7 and f _s = 30.72 Msps. The output of the IDFT are the time domain representation of the length _{T CYC} basic PRACH sequence after OFDM modulation in appropriate SPRACH subcarrier frequency, PRACH subcarrier frequency spacing is equal to that of the other channels in the uplink.

The Z time domain samples output by the IDFT in this embodiment may optionally be repeated to provide a total of Q iterations of the basic SRACH sequence, thereby providing the final SRACH sequence. Step 3008). In other words, in this embodiment, the SRACH sequence of the SRACH preamble is Q repetitions of the basic SRACH sequence, where Q is one or more. The use of multiple iterations improves sensitivity (eg, SINR) and time discrimination (eg, time resolution) after SRACH processing at the base station 76. For example, if Q = 12 and T _CYC = 66.7 μs, then the total length of all the repetitions of the basic SRACH sequence is about 0.8 ms, which is the legacy RACH sequence for configuration 0 of 3GPP LTE Is equivalent to the length of In one embodiment, Q = X · 12, with X = 1 for 3GPP LTE and X> 1 for the frequency scaled version of 3GPP LTE. With repetition, the SRACH sequence of SRACH preamble can be generated continuously for Z · Q samples and effectively extracted at base station 76. Finally, by inserting a CP at the beginning of the Q repetitions of the basic SRACH sequence, a SRACH preamble for transmission is provided (step 3010).

In one embodiment, the time domain SRACH preamble s (t) is defined as follows: 0 ≦ t ≦ Q · T _CYC + T _CP

Here, β _PRACH is, for example, an amplitude scaling factor intended to ensure transmission power (P _SPRACH ) for SPRACH, which may be configured according to existing procedures for setting power of legacy PRACH. x _{u, v} (n) is the v th cyclic shift of the u th root ZC sequence (as per 3GPP LTE standard or similar). φ is a fixed offset relative to the physical RB boundary at the resolution of Δf _SPRACH (eg, 0 or 1). K is equal to 1 for SRACH. T _CP is the CP length of the SRRACH preamble. k ₀ is defined as follows:

Here, the parameter n ^RA _PRB controls the position in the frequency domain, N ^RB _SC is the number of subcarriers per _RB , and N ^UL _RB is the number of RBs in the uplink. Furthermore, the u-th root ZC sequence is defined as follows for 0 ≦ n ≦ N _ZC −1.

Here, u is an index of the ZC physical route sequence. In one embodiment, the SRRACH subcarrier frequency interval (Δf _SPRACH ) is equal to some value Δf in a non-frequency scaled network (eg, Δf _SPRACH = Δf = 15 kHz in 3GPP LTE networks), where Δf is the other of the uplink Equal to the subcarrier spacing of the channel. In another embodiment, the SRACH subcarrier frequency interval (Δf _SPRACH ) is equal to X · Δf in a frequency scaled network (eg, for a frequency scaled version of a 3GPP LTE network with a scaling factor (X) of 10, Δf _SPRACH = X · _Δ f = 10 · 15 kHz = 150 kHz), where X · Δf is the subcarrier spacing of the other channels of the uplink in the frequency scaling network. In particular, the value K is equal to Δf / Δf _SPRACH = 1 for non-frequency scaling networks and X · Δf / Δf _SPRACH = 1 for frequency scaling networks. In either case, K = 1 such that subcarrier spacing uniformity is achieved between the SPRACH and other channels on the uplink.

FIG. 13 is a block diagram of a wireless device 80 operative to generate a SRHACH preamble in accordance with the process of FIG. 12 in accordance with one embodiment of the present disclosure. In particular, FIG. 13 shows only those portions of the wireless device 80 that operate to generate the SRACH preamble. The wireless device 80 includes other components not shown in FIG. The blocks shown in FIG. 13 may be implemented by hardware or may be implemented by a combination of software and hardware. As shown, the wireless device 80 includes a DFT function 82 that operates to perform a DFT of the basic SRACH sequence in the time domain. As discussed above, the length (T _CYC ) of the basic SRACH sequence in the time domain is such that the frequency spacing of the output frequency bins (which is 1 / T _CYC ) is equal to the desired SPRACH subcarrier frequency spacing In that case, the desired SPRACH subcarrier frequency spacing is equal to the subcarrier frequency spacing of the other channels of the uplink. Subcarrier mapping function 84 maps the output of the DFT to the appropriate SPRACH subcarriers. The IDFT function 86 then performs an IDFT of the output of the subcarrier mapping function 84 to provide Z time domain samples as discussed above. The iteration function 88 then repeats the Z time domain samples for a total of Q times. Finally, the CP insertion function 90 inserts a CP to complete the SRACH preamble. The functions 82 to 90 may be implemented by hardware, or may be implemented by a combination of hardware and software.

  FIG. 14 illustrates one embodiment of a base station 76 that operates to detect SRACH sequences transmitted by the wireless device 80 according to one embodiment of the present disclosure. Among other things, as understood by those skilled in the art, base station 76 includes other components not shown in FIG. As illustrated, the base station 76 includes a normal traffic path formed by the data processing unit 92 and the uplink processing function 94, a data processing function 92, an SRACH preamble extraction function 95, a data processing function 96, and an SRACH detection function 98. And the SRACH path formed by The data processing function 92 includes a CP removal function 100, a frequency shift function 102 and a symbol FFT function 104. In some embodiments, frequency shift function 102 may not be included. The CP removal function 100 removes the CP of the received signal. The frequency shift function 102 then shifts the frequency of the received signal by one half of the normal subcarrier spacing (eg, 15/2 kHz = 7.5 kHz for 3GPP LTE). The received signal is then divided into time fragments corresponding to a fraction (e.g. 1/14 or 1/12) of a subframe (which is 1 ms for 3GPP LTE), referred to as a symbol. The symbol FFT function 104 then performs symbol-wise FFT using a 2048 point FFT per symbol for a 20 MHz 3GPP LTE bandwidth. The resulting frequency domain signal fragments are then provided to uplink processing function 94 for further signal processing.

  The output of symbol FFT function 104 for a predetermined number of symbols (e.g., 12) for the SRACH path is input to SRHACH preamble extraction function 95. The details of SRACH preamble extraction function 95 are similar to those described above for device 56 of FIG. 6, but in this example only 71 subcarriers (instead of 839 subcarriers) are used. The output symbols of the SRRACH preamble extraction function 95 are input to the data processing function 96 one by one. Within the scope of data processing function 96, SPRACH subcarrier selection function 106 selects (e.g., 71) outputs of symbol FFT function 104 that correspond to the SPRACH subcarriers used. The correlation function 108 then extracts the temporary identifier of the transmitting wireless device 80 by performing a correlation operation between the output of the SPRACH subcarrier selection function 106 and the known ZC sequence. The IFFT function 110 then performs a 2,048-point IFFT, resulting in a time domain signal, which is then processed by the SRACH detection function 98. In particular, the functions 94 and 98-110 of FIG. 14 may be implemented in hardware or may be implemented in a combination of hardware and software.

  As discussed above, in some embodiments, the basic SRACH sequence is repeated Q times to provide a SRACH sequence of SRACH preambles, for example for the purpose of improving sensitivity and time discrimination at the base station 76. However, in some cases, the base station 76 may be able to detect the SRACH preamble before all repetitions of the basic SRACH sequence Q times have been transmitted. In this regard, FIG. 15 shows the operation of the base station 76 and the wireless device 80 to provide an early stop of transmission of SRACH preambles by the wireless device 80 according to one embodiment of the present disclosure. As shown, the wireless device 80 transmits the SRRACH preamble (step 4000). During transmission of the SRACH preamble, before all Q repetitions of the basic SRACH sequence are transmitted, the base station 76 detects the basic SRACH sequence (step 4002). Upon detecting the basic SRACH sequence, the base station 76 sends a request to the wireless device 80 for an early stop of transmission of the SRACH preamble (step 4004). In response to the request, the wireless device 80 stops transmitting the SRACH preamble before all Q repetitions of the SRACH sequence are transmitted (step 4006).

  For multiple iterations, FIG. 12 above describes the process in which the iterations of the basic SRACH sequence are generated as a continuous signal. FIG. 16 illustrates a process for generating a SRACH preamble in which symbol-by-symbol traffic processing is used to insert a CP for each repetition of a basic SRACH sequence according to another embodiment of the present disclosure. As discussed above, the basic SRACH sequence is generated in the time domain (step 5000), and then by performing DFT (eg, FFT) on the basic SRACH sequence in the time domain, the basic SRACH sequence in the time domain is It is converted into a frequency domain representation of the basic SRACH sequence (step 5002). The output of the DRACH, which is a SRACH subcarrier, is then mapped to the appropriate frequency offset for the SPRACH in the uplink (step 5004). After mapping. The frequency domain samples are converted into Z time domain samples by performing Z points of IDFT (eg, Z points of IFFT) on the frequency domain samples (step 5006).

In this embodiment, CPs of _{Ncp, q} samples are added to Z time domain samples (step 5008). Ncp _{, q} is the number of samples in the CP for the qth iteration of the SRACH sequence. In particular, _{Ncp, q} may be identical for all iterations or may be different for different iterations. Importantly, the Ncp _{, q} sample CP is not part of the SRACH preamble CP. Rather, N _{cp, q} samples are to be made for normal uplink traffic symbols (eg PUSCH symbols) such that the CPs of the N _{cp, q} samples actually form part of the SRACH sequence of the SRACH preamble. It is generated by processing equivalent to A determination is then made as to whether the total number of time domain samples generated for the SRACH sequence is greater than or equal to Q · Z (step 5010). Q is a value of one or more (ie, equal to one if there is one iteration / instance of the basic SRACH sequence, and greater than one if there are more than one iteration / instance of the basic SRACH sequence). If the total number of time domain samples is not greater than or equal to Q · Z, then the counter q is incremented (step 5012) and the process returns to step 5008 to repeat the SRACH sequence and add a CP for the repetition. Once the total number of time domain samples is greater than or equal to Q · Z, generation of the SRACH sequence is complete. And, among other things, the CP of the SRACH preamble is added to complete the SRACH preamble.

In one embodiment, the SRAH preamble s (t _s , q) in the time domain is defined as 0 ≦ q <Q, 0 ≦ t ≦ Q · T _CYC + T _CP as follows:

Here, β _PRACH is, for example, an amplitude scaling factor intended to ensure transmission power (P _SPRACH ) for SPRACH, which may be configured according to existing procedures for setting power of legacy PRACH. x _{u, v} (n) is the v th cyclic shift of the u th root ZC sequence (as per 3GPP LTE standard or similar). φ is a fixed offset relative to the physical RB boundary at the resolution of Δf _SPRACH (eg, 0 or 1). K is equal to 1 for SRACH. T _CP is a total length of CPs of SRACH preambles. T _{CP, q} is the N _{cp, q} sample CP time length for the q th traffic symbol used to generate the SRACH preamble.

Here, the parameter n ^RA _PRB controls the position in the frequency domain, N ^RB _SC is the number of subcarriers per _RB , and N ^UL _RB is the number of RBs in the uplink. Furthermore, the u-th root ZC sequence is defined as follows for 0 ≦ n ≦ N _ZC −1.

Here, u is an index of the ZC physical route sequence. In one embodiment, the SRRACH subcarrier frequency interval (Δf _SPRACH ) is equal to some value Δf in a non-frequency scaled network (eg, Δf _SPRACH = Δf = 15 kHz in 3GPP LTE networks), where Δf is the other of the uplink Equal to the subcarrier spacing of the channel. In another embodiment, the SRACH subcarrier frequency interval (Δf _SPRACH ) is equal to X · Δf in a frequency scaled network (eg, for a frequency scaled version of a 3GPP LTE network with a scaling factor (X) of 10, Δf _SPRACH = X · _Δ f = 10 · 15 kHz = 150 kHz), where X · Δf is the subcarrier spacing of the other channels of the uplink in the frequency scaling network. In particular, the value K is equal to Δf / Δf _SPRACH = 1 for non-frequency scaling networks and X · Δf / Δf _SPRACH = 1 for frequency scaling networks. In either case, K = 1 such that subcarrier spacing uniformity is achieved between the SPRACH and other channels on the uplink. In particular, in the equation for s (t _s , q) above, the additional term ^q _{q q = 0} T _{CP, q} is the discontinuity of the block of Z time domain samples due to the addition of CP samples Phase shift added to compensate for the sex.

  FIG. 17 is a block diagram of the base station 76 of FIG. 7 in accordance with one embodiment of the present disclosure. The present description is equally applicable to other types of wireless access nodes (ie, nodes within the wireless access network of cellular communication network 74). As illustrated, base station 76 includes a baseband unit 112 including one or more processors 114, a memory 116 and a network interface 118, and a radio unit 120 including a transceiver 122 coupled to one or more antennas 124. ,including. In one embodiment, the functionality of the SRACH processing of base station 76 described above is at least partially implemented in baseband unit 112 in the form of software executed by processor 114, which are The processors may be distributed within or associated with the baseband unit 112, or may be distributed across two or more network nodes (eg, baseband unit 112 and other network nodes). In another example, processor 114 includes one or more hardware components (eg, application specific integrated circuits (ASICs)) that provide some or all of the above-described SRACH processing functionality. In other embodiments, processor 114 includes one or more hardware components (e.g., CPUs (Central Processing Units)), and some or all of the SRACH processing functionality described above is stored, for example, in memory 116 And implemented by the processor 114.

  FIG. 18 is a block diagram of the wireless device 80 of FIG. 7 in accordance with one embodiment of the present disclosure. As shown, wireless device 80 includes a transceiver 130 coupled to processor 126, memory 128 and one or more antennas 132. Processor 126 includes one or more hardware processing components such as, for example, one or more CPUs or one or more ASICs. In one embodiment, the functionality of the SRACH processing of wireless device 80 described above is implemented at least partially within processor 126. For example, in one embodiment, processor 126 includes one or more hardware components (e.g., one or more ASICs) that provide some or all of the SRACH processing functionality described above. In other embodiments, processor 126 includes one or more hardware components (e.g., a CPU or itself consisting of a plurality of processors), and some or all of the SRACH processing functionality described above, for example, memory Implemented in software stored within 128 and executed by processor 126.

  Systems and methods for transmission of SRACH preambles and reception / detection of SRACH sequences are disclosed herein. With regard to the specific benefits or advantages, rather than limitations, at least some non-limiting benefits and advantages of the embodiments described herein are as follows. As discussed above, the subcarrier frequency spacing of the SPRACH is equal to the subcarrier frequency spacing of the other channels on the uplink. As a result, the SPRACH subcarriers are orthogonal to the subcarriers of the other channels on the uplink. This orthogonality to the other uplink channel subcarriers provides improved SINR and system performance. In addition, transmission is achieved by eliminating the need for super FFT / IFFT by using the same subcarrier frequency spacing as other uplink channels, rather than the smaller 3GPP LTE RACH subcarrier frequency spacing. The complexity of SRACH preamble generation on the side and SRACH sequence detection / reception on the receiving side is substantially reduced. As another example, software and / or hardware utilized to generate other uplink channels (eg, PUSCH) can be used to generate SPRACH.

The following acronyms are used throughout the disclosure.
・ 3GPP 3rd Generation Partnership Project
・ 4G 4th Generation
・ 5G 5th Generation
・ ASIC Application Specific Integrated Circuit
・ CP Cyclic Prefix
・ CPU Central Processing Unit
・ DFT Discrete Fourier Transform
・ DRS Demodulation Reference Signal
-ENB Evolved Node B
・ FFT Fast Fourier Transform
· GHz Gigahertz
・ IDFT Inverse Discrete Fourier Transform
・ IFFT Inverse Fast Fourier Transform
・ ISI Inter-Symbol Interference
· KHz Kilohertz
・ Km Kilometer
・ LTE Long Term Evolution
・ MHz Megahertz
Ms Millisecond
・ Msps Mega samples per Second
・ OFDM Orthogonal Frequency Division Multiplexing
・ PRACH Physical Random Access Channel
・ PSS Primary Synchronization Signal
・ PUCCH Physical Uplink Control Channel
・ PUSCH Physical Uplink Shared Channel
・ RACH Random Access Channel
・ RB Resource Block
・ RRC Radio Resource Control
・ SINR Signal-to-Interference plus Noise Ratio
・ SPRACH Simple Physical Random Access Channel
・ SRACH Simple Random Access Channel
・ SRS Sounding Reference Signal
・ SSS Secondary Synchronization Signal
・ UE User Equipment
・ Μs Microsecond
・ ZC Zadoff-Chu

  Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.

Claims (25)

A method of operating a wireless device (80) for performing random access in a cellular communication network (74), the method comprising:
From the wireless device (80) to the radio access node (76) in the cellular communication network (74), in uplink, subcarrier frequency spacing equal to subcarrier frequency spacing in one or more other channels of the uplink Transmitting a random access preamble on a physical random access channel comprising a plurality of subcarriers having
Receiving a random access response from the wireless access node (76) in response to the transmission of the random access preamble;
Method including.   The method of claim 1, wherein the cellular communication network (74) is a Long Term Evolution (LTE) cellular communication network.   3. The method of claim 1 or claim 2, wherein the one or more other channels of the uplink comprise a physical uplink shared channel.   The subcarrier frequency spacing of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink is 15 kilohertz. Section method.   The subcarrier frequency spacing of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink is X · 15 kHz, where X> 1. The method of any one of 1-2. Sending the random access preamble may
Generating a basic random access sequence having a length equal to or less than the number of subcarriers in the physical random access channel;
Providing a frequency domain representation of the basic random access sequence by converting the basic random access sequence from time domain to frequency domain;
The mapped frequency domain representation of the random access sequence by mapping the frequency domain representation of the basic random access sequence to the appropriate frequency offset for the physical random access channel within the uplink system bandwidth. To provide and
Z number of random access sequences for the random access preamble for one symbol period of the physical random access channel by converting the mapped frequency domain representation of the basic random access sequence from the frequency domain to the time domain To provide a sample of
The method of any one of claims 1 to 5 comprising   Transmitting the random access preamble may repeat the Z samples of the random access sequence for the random access preamble by one or more additional symbol periods of the physical random access channel. The method of claim 6, further comprising. The number of samples Z of the random access sequence for the random access preamble is defined as the product of the time length of the basic random access sequence and the system sample rate dependent on the system bandwidth of the uplink;
Transmitting the random access preamble may repeat the Z samples of the random access sequence for the random access preamble for Q symbol periods of the physical random access channel, where Q is 2 or more. , And further,
The method of claim 6. Sending the random access preamble may
Inserting, for the one symbol period of the physical random access channel, a certain number of cyclic prefix samples at the beginning of the Z samples of the random access sequence for the random access preamble; The cyclic prefix sample of is a part of the random access sequence of the random access preamble, rather than a cyclic prefix for the random access preamble.
Repeating the Z samples of the random access sequence for the random access preamble for a second symbol period of the physical random access channel;
Inserting, for the second symbol period of the physical random access channel, a certain number of cyclic prefix samples at the beginning of the Z samples of the random access sequence for the random access preamble;
The method of claim 6, further comprising During transmission of the random access preamble,
Receiving from the radio access node (76) a request for an early stop of transmission of the random access preamble;
Stopping transmission of the random access preamble in response to receiving the request;
The method of claim 7 or claim 8 further comprising   The bandwidth of the physical random access channel is 1.08 megahertz, and the subcarriers of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink are The method of any one of claims 6 to 10, wherein the frequency interval is 15 kilohertz and the length of the random access sequence is 72 or less.   The method of claim 11, wherein the basic random access sequence is a Zadoff-Chu (ZC) sequence, and the length of the random access sequence is 71.   The bandwidth of the physical random access channel is X · 1.08 MHz, and the sub-carriers of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink are The method according to any one of claims 6 to 10, wherein the carrier frequency interval is X · 15 kHz, where X> 1, and the length of the basic random access sequence is 72 or less.   The method of claim 13, wherein the basic random access sequence is a Zadoff-Chu (ZC) sequence, and the length of the basic random access sequence is 71.   The bandwidth of the physical random access channel is X · M · 15 kHz, and the sub-carriers of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink are The method according to any one of claims 6 to 10, wherein the carrier frequency interval is X · 15 kHz, where X> 1, and the length of the basic random access sequence is M or less.   The method of claim 15, wherein the basic random access sequence is a Zadoff-Chu (ZC) sequence, and the length of the basic random access sequence is a largest prime number less than or equal to M. A transceiver (130),
A processor (126) associated with the transceiver (130);
A wireless device (80) comprising
The processor (126)
From the wireless device (80) to the radio access node (76) in the cellular communication network (74) via the transceiver (130), in the uplink, in one or more other channels of the uplink. Transmitting a random access preamble on a physical random access channel comprising a plurality of subcarriers with subcarrier frequency spacing equal to the carrier frequency spacing;
Receiving a random access response from the radio access node (76) in response to the transmission of the random access preamble via the transceiver (130);
Configured as
Wireless device (80).   The wireless device (80) of claim 17, wherein the cellular communication network (74) is a Long Term Evolution (LTE) cellular communication network.   19. The subcarrier frequency spacing of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink is 15 kilohertz. Section wireless device (80).   The subcarrier frequency spacing of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink is X · 15 kHz, where X> 1. The wireless device (80) of any of clauses 17-18. The processor (126) may transmit the random access preamble.
Generating a basic random access sequence having a length equal to or less than the number of subcarriers in the physical random access channel;
Providing a frequency domain representation of the basic random access sequence by converting the basic random access sequence from time domain to frequency domain;
A mapped frequency domain representation of the basic random access sequence by mapping the frequency domain representation of the basic random access sequence to an appropriate frequency offset for the physical random access channel within the uplink system bandwidth. To provide
Providing a sample of a random access sequence of the random access preamble for one symbol period of the physical random access channel by converting the mapped frequency domain representation of the basic random access sequence from the frequency domain to the time domain ,
21. The wireless device (80) of any one of claims 17-20, configured as follows.   Sending the random access preamble further comprises: repeating the samples of the random access sequence of the random access preamble over one or more additional symbol periods of the physical random access channel. 21 wireless devices (80). The processor (126) may, during transmission of the random access preamble,
Receiving from the radio access node (76) a request for an early stop of transmission of the random access preamble via the transceiver (130);
Stopping transmission of the random access preamble in response to receiving the request;
23. The wireless device (80) of claim 22, further configured as follows.   The bandwidth of the physical random access channel is 1.08 megahertz, and the subcarriers of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink are 24. The wireless device (80) of any of claims 21-23, wherein the frequency spacing is 15 kilohertz and the length of the basic random access sequence is 72 or less.   The bandwidth of the physical random access channel is X · 1.08 MHz, and the sub-carriers of both the plurality of subcarriers in the physical random access channel and the subcarriers in the one or more other channels of the uplink are A wireless device (80) according to any of claims 21 to 23, wherein the carrier frequency interval is X · 15 kilohertz, where X> 1, and the length of the basic random access sequence is 72 or less.

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