HK1235970B - Enhanced remote radio head and computer readable storage medium - Google Patents

Description

Enhanced remote radio head and computer readable storage medium

Technical Field

The present disclosure relates to cloud radio access networks.

Background Art

As mobile devices (e.g., cell phones and tablet computers) have become increasingly popular in recent years, the demand for wireless communications has increased. To meet this demand, an ever-increasing number of base stations have been deployed in radio access networks (RANs). Because many of the devices wirelessly connected to the RAN are mobile, the network traffic load at a given base station can vary throughout a typical day as users carry their mobile devices to different locations.

Summary of the Invention

According to a first aspect of the present disclosure, an enhanced remote radio head (eRRH) is provided, which may be configured for use in a cloud-based radio access network (C-RAN), wherein baseband physical layer processing is separated between a baseband processing unit (BBU) pool and the eRRH. The eRRH comprises: one or more processors; an analog front end (AFE) configured to receive a radio signal from at least one user equipment (UE) via one or more antennas; an analog-to-digital converter (ADC) configured to receive the radio signal from the AFE and digitize the radio signal; a control/data separator module configured to: receive the digitized radio signal from the ADC; perform cyclic prefix removal on the digitized radio signal using the one or more processors; and identify a plurality of time-domain physical uplink shared channel (PUSCH) phase/quadrature I/Q samples in the digitized radio signal, wherein the plurality of time-domain PUSCH I/Q samples correspond to a plurality of PUSCH I/Q symbols. The I/Q symbols are associated with physical resource blocks (PRBs); a fast Fourier transform (FFT) module configured to receive the multiple time-domain PUSCH I/Q samples from the control/data separator module and perform a fast Fourier transform on the multiple time-domain PUSCH I/Q samples to generate a plurality of frequency-domain PUSCH I/Q samples corresponding to the multiple PUSCH I/Q symbols; a bit allocation module configured to: receive user scheduling side information from the BBU pool via a fronthaul link, the user scheduling side information being associated with the PRBs, wherein the user scheduling side information includes one or more of the following items: constellation or modulation of each subcarrier, turbo coding rate, number of users scheduled in multiple-input multiple-output (MIMO), hybrid automatic repeat request (HARQ) state, target signal-to-interference-plus-noise ratio (SINR), or average bit/block error performance; and identify a PUSCH to be allocated to each of the multiple PUSCH I/Q symbols based on the user scheduling side information. a number of bits for an I/Q symbol; and a compression module configured to: receive the plurality of frequency-domain PUSCH I/Q samples from the FFT module; receive the number of bits for each PUSCH I/Q symbol in the plurality of PUSCH I/Q symbols from the bit allocation module; and perform lossy compression in which each of the plurality of frequency-domain PUSCH I/Q samples corresponding to the plurality of PUSCH I/Q symbols is normalized and quantized based on the number of bits received from the bit allocation module.

According to a second aspect of the present disclosure, a computer-readable storage medium storing one or more programs may include instructions for performing the following items when executed by one or more processors: receiving a radio signal at an enhanced remote radio head (eRRH); performing cyclic prefix removal on the radio signal at the eRRH; identifying a plurality of time-domain physical uplink shared channel (PUSCH) phase/quadrature I/Q samples in the radio signal, the plurality of time-domain PUSCH I/Q samples corresponding to a plurality of PUSCH I/Q symbols, wherein the plurality of PUSCH I/Q symbols are associated with physical resource blocks (PRBs) in the radio signal; performing fast Fourier transform on the plurality of time-domain PUSCH I/Q samples at the eRRH to generate a plurality of frequency-domain PUSCH corresponding to the plurality of PUSCH I/Q symbols. receiving, at the eRRH, user scheduling information from a BBU pool or an evolved Node B (eNB) via a fronthaul link, the user scheduling information being associated with the PRB, wherein the scheduling information includes one or more of the following: a constellation or modulation of each subcarrier, a turbo coding rate, a number of users scheduled in a multiple-input multiple-output (MIMO) scheme, a hybrid automatic repeat request (HARQ) state, a target signal-to-interference and noise ratio (SINR), or an average bit/block error performance; identifying, at the eRRH, a specified number of bits to be used for each of the multiple PUSCH I/Q symbols based on the user scheduling information; normalizing, at the eRRH, each of the multiple frequency-domain PUSCH I/Q samples, the multiple frequency-domain PUSCH I/Q samples corresponding to the multiple PUSCH I/Q symbols; and performing lossy frequency-domain compression at the eRRH, in which each of the multiple frequency-domain PUSCH I/Q samples is discretized based on the specified number of bits.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present disclosure will be apparent from the following detailed description taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the present disclosure; and wherein:

Figure 1 illustrates the C-RAN architecture based on an example;

FIG2 illustrates a C-RAN architecture based on a Common Public Radio Interface (CPRI) according to an example;

Figure 3 illustrates a PHY-split C-RAN architecture based on an example;

FIG4 illustrates a diagram of an enhanced remote radio head (eRRH), according to an example;

FIG5 is a flow chart illustrating exemplary functionality of an eRRH, according to an example; and

FIG6 provides an illustration of a wireless device, according to an example.

Reference will now be made to the illustrated exemplary embodiments, and specific language will be used to describe the same, but it will be understood that no limitation in scope is intended thereby.

DETAILED DESCRIPTION

Before disclosing and describing some embodiments, it should be understood that the claimed subject matter is not limited to the specific structures, process operations or materials disclosed herein, but extends to equivalents thereof recognized by those of ordinary skill in the relevant art. It should also be understood that the terminology employed herein is used solely for the purpose of describing specific examples and is not intended to be limiting. The same reference numerals in different figures represent the same elements. The numbers provided in the flow charts and processes are provided for clarity of illustration and do not necessarily indicate a particular order or sequence.

The following provides a preliminary overview of the embodiments, and then describes specific technical embodiments in more detail later. This preliminary overview is intended to help readers understand the technology more quickly, but is not intended to identify the key features or essential features of the technology nor to limit the scope of the claimed subject matter.

As mobile devices with wireless capabilities have become increasingly popular, the demand for wireless communications has grown rapidly in recent years. Many of these mobile devices provide convenient functionality (e.g., Internet access, voice calls, and text messaging) that relies on connectivity to wireless networks. As mobile devices have become more ubiquitous, traffic through the wireless networks that serve these mobile devices has increased significantly.

The increase in traffic through wireless networks has challenged the traditional radio access network (RAN) paradigm. The cost of building, upgrading, and maintaining traditional base station (BS) sites to meet the growing customer demand for wireless traffic is high in terms of capital expenditure (CAPEX) and operating expense (OPEX) amounts. This problem is further amplified because the peak-to-average ratio of network load is typically high. For example, BSs in most residential suburban areas may experience a peak load of wireless traffic during a brief period in the early morning before residents leave for work in nearby cities, but may experience very low loads during most of the day until residents return in the evening. In this type of scenario, the network resources of the BS are underutilized for most of the day.

To address these issues that arise in traditional RAN infrastructure, a centralized processing cloud-based RAN (Cloud (C)-RAN) infrastructure has been proposed. In C-RAN, unlike traditional cellular systems, a central pool of baseband processing units (BBUs) performs most of the baseband processing, while remote radio heads (RRHs) perform the transmission and reception of radio signals. The C-RAN architecture can improve energy efficiency by consolidating energy-consuming hardware devices at the BBU pool. The C-RAN architecture can also reduce both the CAPEX and OPEX of the network by making centralized network management and network upgrades easy to accomplish. In addition, the C-RAN architecture can be used to implement advanced coordinated multi-point (CoMP) communications and interference-management schemes such as enhanced inter-cell interference coordination (eICIC).

FIG1 illustrates a typical C-RAN architecture 100. RRHs 102, 104, and 106 can transmit and receive wireless signals from wireless-capable devices, such as user equipment (UE). RRHs 102, 104, and 106 can communicate with a BBU pool 114 via fronthaul links 116, 118, and 120, respectively. A Common Public Radio Interface (CPRI) can be a type of interface used to connect RRHs 102, 104, and 106 to the BBU pool 114 via fronthaul links 116, 118, and 120. The BBU pool 114 can communicate with a core network 122. In one example, communications from the core network 122 to a wireless device 124 within the coverage area of RRH 102 (or RRH 104 or RRH 106) can be sent from the core network 122 to the BBU pool 114. BBU pool 114 may then transmit the communication to RRH 102 (RRH 104 or RRH 106) via fronthaul link 116 (or fronthaul link 118 or fronthaul link 120, respectively). The communication may then be transmitted from RRH 102 (RRH 104 or RRH 106) via radio signals to wireless device 124. This is generally referred to as downlink communication.

In another example, communications from wireless device 124 to the core network, referred to as uplink communications, may be sent from wireless device 124 and received via radio signals at RRH 102 (RRH 104 or RRH 106). RRH 102 (RRH 104 or RRH 106) may send the communications via fronthaul link 116 (or fronthaul link 118 or fronthaul link 120, respectively) to BBU pool 114. BBU pool 114 may then send the communications to core network 122, where the communications may be directed to their intended destination.

FIG2 illustrates an example of a CPRI-based C-RAN architecture 200 in which a BBU pool 202 is connected to an RRH 204 by a fronthaul link 206. The RRH 204 may include an analog front end (AFE) 208, a digital-to-analog converter (DAC) 210, and an analog-to-digital converter (ADC) 212. The AFE 208 may be operably connected to a plurality of antennas 228. Furthermore, as shown in option 214, the RRH 204 may include at least two modules for CPRI processing: a compression and framing module 216 and a decompression and framing module 218. The BBU pool 202 may include a layer processing module 220 that handles processing of the packet data convergence protocol (PDCP), radio link control (RLC), medium access control (MAC), and physical (PHY) layers. As shown in option 222, the BBU pool 202 may also include at least two modules for CPRI processing: a compression and framing module 224 and a decompression and framing module 226.

In one example, in downlink communications, a signal may be sent from the layer processing module 220 of the BBU pool 202 to the compression and framing module 224 of the BBU pool 202. The compression and framing module 224 may perform time-domain compression and framing operations on the signal and send the signal to the decompression and framing module 218 of the RRH 204 via the fronthaul link 206 using the CPRI protocol. The decompression and framing module 218 may perform compression and framing operations on the signal and send the signal to the DAC 210. The DAC 210 may convert the signal into an analog signal and send the analog signal to the AFE 208. The AFE may transmit the analog signal to the plurality of antennas 228. The plurality of antennas 228 may wirelessly transmit the analog signal to a destination device (e.g., a UE).

In another example, in uplink communications, multiple antennas 228 may receive radio signals and communicate the signals to AFE 208. AFE 208 may communicate the signals to ADC 212. ADC 212 may digitize the signals using phase (I) and quadrature (Q) sampling and send the digitized signals to compression and framing module 216. Compression and framing module 216 may perform time-domain compression and framing operations on the signals and pass the signals to decompression and framing module 226 of BBU pool 202 via fronthaul link 206 using the CPRI protocol. Decompression and framing module 226 may decompress and frame the signals and send the signals to layer processing module 220. Layer processing module 220 may perform higher-layer baseband processing on the signals.

While the C-RAN paradigm alleviates many of the issues associated with the traditional RAN paradigm, existing C-RAN architectures also introduce some new challenges. In particular, because existing C-RAN paradigms require a CPRI interface for connecting the RRHs to the BBU pool, the transfer rate requirements for the fronthaul link used in the C-RAN architecture can be problematic because the expected transfer rate on the fronthaul interface (i.e., the fronthaul rate) can be significantly higher than the rate at which data is transferred on the radio interface.

For example, consider a Long Term Evolution (LTE) uplink (UL) system with a 10 megahertz (MHz) bandwidth, two receive antennas at the RRH, and a sampling frequency of 15.36 MHz. If a 15-bit representation of the I/Q phase digital samples is used, the I/Q data rate is 921.6 megabits per second (Mbps). If the CPRI basic frame overhead of one header byte for every 15 bytes of data and a line coding rate of 10/8 are considered, the physical line rate becomes 1.2288 gigabits per second (Gbps). Furthermore, the total CPRI physical line rate increases linearly with the number of antennas, and the system bandwidth can quickly exceed 10 Gbps when carrier aggregation is used. These factors can therefore lead to fronthaul rate requirements that are too high for practical deployments.

Other issues also impact existing C-RAN architectures. For example, the sampling rate of CPRI is the same as that of LTE and is independent of user load or activity within the cell; therefore, there is no statistical averaging gain. Furthermore, most CPRI data rate requirements are driven by I/Q user-plane data samples. Due to the use of guard bands, LTE signals are inherently redundant. For example, in a 10 MHz LTE system, only 600 of the 1024 available subcarriers are used for data; the remaining subcarriers are cleared to zero for guard bands. However, while time-domain I/Q samples have excess signal structure, complex nonlinear schemes are required to exploit this redundancy in order to achieve high compression factors. Furthermore, fronthaul compression schemes operating on time-domain I/Q samples cannot exploit the signal-to-quantization-to-noise ratio (SQNR) for different modulation and coding schemes or user scheduling information (e.g., user activity, subcarrier occupancy), as this information is generally lost once the signal is separated in the time domain. For at least these reasons, compression performance in existing C-RAN architectures is relatively poor.

Systems and methods according to the present disclosure propose an alternative C-RAN architecture (i.e., a PHY-split C-RAN architecture) in which baseband physical layer processing is split between a pool of BBUs and enhanced RRHs (eRRHs). A frequency domain compression method that leverages LTE signal redundancy and user scheduling information can be used at the eRRH to significantly reduce fronthaul data rate requirements. In some examples consistent with the present disclosure, uniform scalar quantization is used in conjunction with variable rate Huffman coding for the frequency domain compression method. In some examples, the frequency domain compression method includes lossless compression followed by lossy compression. In some examples, portions of the architecture for compression are separable, thereby enabling low-complexity hardware implementations.

FIG3 is an illustration of a PHY-split C-RAN architecture 300, according to an example. A BBU pool 302 is connected to an enhanced RRH (eRRH) 304 via a fronthaul link 306. The eRRH 304 may include an analog front end (AFE) 308, a digital-to-analog converter (DAC) 310, and an analog-to-digital converter (ADC) 312. The AFE 308 may be operably connected to a plurality of antennas 328. Furthermore, as shown in option 314, the eRRH 304 may include two modules that perform some limited baseband physical layer processing: an uplink baseband physical layer processing (UBPHY) module 316 and a downlink baseband physical layer processing (DBPHY) module 318. The BBU pool 302 may include a layer processing module 320 that handles processing of the packet data convergence protocol (PDCP), radio link control (RLC), medium access control (MAC), and physical (PHY) layers. As shown in option 322 , the BBU pool 302 may also include at least two additional processing modules: a compression and framing module 324 and a decompression and framing module 326 .

In one example, uplink radio signals may be received via multiple antennas 328 and communicated to AFE 308. AFE 308 may communicate the signals to ADC 312. ADC 312 may digitize the signals using phase (I) and quadrature (Q) sampling and send the digitized signals to UBPHY module 316. UBPHY module 316 may perform some physical (PHY) layer processing functions on the uplink signals, such as cyclic prefix (CP) removal and fast Fourier transform (FFT) calculation. UBPHY module 316 may also perform compression and framing operations on the signals and pass them to decompression and framing module 326 of BBU pool 302 via fronthaul link 306. Decompression and framing module 326 may decompress and frame the signals and send them to layer processing module 320. Layer processing module 320 may perform higher-layer baseband processing on the signals not already performed by UBPHY module 316, such as channel estimation, turbo encoding/decoding, and multi-antenna processing.

In one example, a downlink signal may be received from the core network by layer processing module 320 from BBU pool 302 of the core network. Layer processing module 320 may send the signal to compression and framing module 324 of BBU pool 202. Compression and framing module 224 may compress and frame the signal and send it to DBPHY module 318 of RRH 304 via fronthaul line 306. DBPHY module 318 may perform some PHY layer processing functions on the downlink signal that layer processing module 320 does not previously perform, such as adding a cyclic prefix (CP) and calculating an inverse fast Fourier transform (IFFT). DBPHY module 318 may also decompress and frame the signal and send it to DAC 310. DAC 310 may convert the signal into an analog signal and send the analog signal to AFE 308. The AFE may transmit the analog signal to multiple antennas 328. Multiple antennas 328 may wirelessly transmit the analog signal to a destination device (e.g., a UE).

In some examples consistent with the present disclosure (e.g., using LTE), the allocation of time-frequency resources among multiple users and user scheduling information for both downlink (DL) and uplink (UL) are available at the BBU pool. Some examples of user scheduling information include, but are not limited to, occupied subcarriers, clustering or modulation of individual subcarriers, turbo coding rate, number of users scheduled in multiple-input multiple-output (MIMO), hybrid automatic repeat request (HARQ) state, target signal-to-interference and noise ratio (SINR), and average bit/block error performance.

In an example consistent with the present disclosure, user scheduling information can be used to achieve the desired compression of I/Q data samples flowing through the fronthaul link. For reliable encoding of baseband information, the target SQNR generally varies based on the modulation and coding scheme used. Therefore, the number of bits allocated to quantize resource blocks carrying orthogonal phase shift keying (QPSK) symbols can be significantly less than the number of bits allocated to quantize resource blocks carrying 64-quadrature amplitude modulation (64-QAM) symbols.

FIG4 illustrates a diagram of an enhanced remote radio head (eRRH) 400, according to an example. The eRRH 400 may include an analog front end (AFE) 402 operatively connected to a plurality of antennas 404. The AFE 402 may receive radio signals from/via the plurality of antennas 404. The AFE 402 may communicate the received uplink signals to a DAC/ADC module 406. The DAC/ADC module 406 may include an analog-to-digital converter (ADC) and/or a digital-to-analog converter (DAC). The DAC/ADC module 406 may digitize the signals using phase (I) and quadrature (Q) sampling and send the digitized signals to a control/data separator module 408. In some embodiments, the digitized signals may include time-domain I/Q samples.

The control/data separator module 408 may remove the cyclic prefix (CP) from the digitized signal and separate the user-plane data symbols (i.e., physical uplink shared channel (PUSCH) I/Q symbols) in the digitized signal from non-data symbols in the digitized signal, such as reference signals, physical uplink control channel (PUCCH) symbols, and random access channel (RACH) signals. In some embodiments, the user-plane data symbols may be represented by multiple time-domain I/Q samples. The control/data separator module 408 then transmits the user-plane data symbols (i.e., PUSCH I/Q symbols) to a fast Fourier transform (FFT) module 410 and transmits the reference signals, physical uplink control channel (PUCCH) symbols, and random access channel (RACH) signals to a packing and formatting module 412. The FFT module 410 may perform an FFT on the user-plane data symbols (i.e., PUSCH I/Q symbols) by calculating the FFT and transmit the user-plane data symbols (i.e., PUSCH I/Q symbols) to a compression module 414. More specifically, in some embodiments, the FFT module 410 may perform an FFT on a plurality of time-domain I/Q samples representing user-plane data symbols to generate a plurality of frequency-domain I/Q samples representing user-plane data symbols.

The bit allocation module 416 can receive side information of an orthogonal frequency division multiple access (OFDMA) uplink signal from the BBU pool via the fronthaul link 418. The side information may include the modulation and coding scheme used per physical resource block (PRB), the number of multiple input multiple output (MIMO) connections, the CoMP scheme, the number of users scheduled on a specific PRB, and/or the HARQ state. In one embodiment, the bit allocation module 416 can allocate a number of quantized bits to be used by the compression module 414 to quantize each symbol in a given PRB based on the side information corresponding to the given PRB. The bit budget applied by the bit allocation module 416 can be a function of the side message and can be a constant for all symbols within a given PRB. Various bit budget schemes can be used. In some instances, the bit budget can be based on the modulation order, as shown in the following table:

Modulation order Bits allocated per actual symbol QPSK 4 16-QAM 5 64-QAM 6

The bit allocation module 416 can communicate the number of bits used to quantize each symbol in a given PRB to the compression module 414. The compression module 414 can normalize the PUSCH I/Q samples (e.g., frequency-domain PUSCH I/Q samples) corresponding to the PUSCH I/Q symbols received from the FFT module on a per-PRB basis by subtracting a mean value and using a scaling value, thereby causing the normalized I/Q samples to have values within a range of -1 to 1. The compression module 414 can include a uniform scalar quantizer for implementing lossy compression, in which the normalized I/Q samples are quantized to a finite number of bits. The number of bits used for each normalized I/Q sample can be consistent with the bit budget provided by the bit allocation module 416 for the PRB to which each corresponding normalized I/Q sample belongs. The lossy compression can produce uniformly quantized normalized I/Q samples that represent the information present in the PUSCH I/Q symbols.

Using scheduling-side information to determine the bit allocation level per PRB can significantly reduce the amount of data sent over the fronthaul link 418 by achieving a higher data compression rate. For example, in one example, testing and simulations have shown that by using the scheduling-side information described herein along with other compression techniques, a tenfold (10×) compression rate is possible. The higher compression level enables the C-RAN architecture to be more easily implemented by reducing bottlenecks occurring at the fronthaul link.

The compression module 414 can also perform lossless compression by compressing the two most significant bits (MSBs) of each uniformly quantized normalized I/Q sample using a lossless, prefix-free Huffman code. In one example, the Huffman code can be defined by the following table:

MSB Code bit 00 0 01 10 10 110 11 111

In the distribution of the MSBs present in quantized normalized I/Q samples (e.g., samples taken from an LTE signal using guard bands), the value 00 may be more common for the first two MSBs than the values 10, 10, and 11. Thus, the lossless compression performed by the compression module 414 may reduce the number of bits required to represent the uniformly quantized normalized I/Q samples. The lossless compression may produce quantized magnitude bits that represent the information present in the uniformly quantized normalized I/Q samples. The compression module 414 may then send the quantized magnitude bits and a sign bit corresponding to each quantized normalized I/Q sample, along with a scale value and an average value for each PRB, to the packing and formatting module 412.

The packing and formatting module 412 may pack and format the reference signals, physical uplink control channel (PUCCH) symbols, and random access channel (RACH) signals received from the control/data separator module 408. Furthermore, the packing and formatting module 412 may pack and format the quantized magnitude bits, sign bits, scaling values, and average values received from the compression module 414. The packing and formatting module 412 may send one or more communications including the packed and formatted quantized magnitude bits, sign bits, scaling values, and average values to the BBU pool via the fronthaul link 418.

While FIG4 provides an exemplary diagram of an eRRH, other eRRH models, designs, and configurations are possible. For example, in some embodiments, several modules shown as separate in FIG4 may also be represented as a single module, depending on the level of abstraction employed. For example, at one level of abstraction, the DAC/ADC module 406, the control/data separator module 408, and the FFT module 410 may be represented as a single module (e.g., a pre-processing module) that implements the functionality described for the three separate modules.

4 may also be represented as separate modules, depending on the level of abstraction employed. For example, compression module 414 may also be represented as a first (lossy) compression module and a second (lossless) compression module, as separate hardware and/or software may be used for lossy compression and lossless compression, respectively.

4 , additional modules may also be included in some eRRH modules. For example, an optional intermediate processing module that can compress and/or decode reference signals, physical uplink control channel (PUCCH) symbols, and/or random access channel (RACH) signals sent from the control/separator module 408 may be inserted in the path between the control/data separator module 408 and the encapsulation and formatting module 412.

In some eRRH models consistent with the present disclosure, the order of some operations performed may vary. For example, in some eRRH models, the FFT of the received signal may be calculated before separating the user plane data symbols and the reference signal.

FIG5 is a flow chart illustrating exemplary functionality 500 of an eRRH capable of reducing fronthaul data rate requirements in a PHY-split C-RAN. The functionality may be implemented as a method or as instructions executable on a machine, where the instructions are embodied on at least one computer-readable medium or a non-transitory machine-readable storage medium. As in 510, a radio signal may be received at an eRRH from at least one UE. In some examples, the radio signal may be digitized by an ADC. As in 520, cyclic prefix removal may be performed on the radio signal at the eRRH; in some examples, the cyclic prefix removal may be performed by a control/data separator module at the eRRH. As in 530, a plurality of PUSCH I/Q symbols associated with a PRB in the radio signal may be identified at the eRRH. In some examples, the PUSCH I/Q symbols may be identified by the control/data separator module (e.g., by identifying a plurality of time-domain I/Q samples corresponding to the PUSCH I/Q symbols). As in 540, an FFT may be performed on the plurality of time-domain I/Q samples representing the plurality of PUSCH I/Q symbols at the eRRH. In some examples, the FFT may be performed at the eRRH by an FFT module.

As in 550, user scheduling side information associated with the PRBs may be received at the eRRH from a BBU pool or an evolved Node B (eNB) via a fronthaul link. In some instances, the user scheduling side information may be received by a bit allocation module at the eRRH. The user scheduling side information may include one or more of the following: user activity, subcarrier occupancy, clustering or modulation of individual subcarriers, turbo coding rate, number of users scheduled in multiple-input multiple-output (MIMO), hybrid automatic repeat request (HARQ) status, target signal-to-interference-and-noise ratio (SINR), and average bit/block error performance.

As in 560, the number of bits allocated to each PUSCH I/Q symbol in the plurality of PUSCH I/Q symbols may be identified based on the user scheduling information (e.g., based on the modulation order included in the user scheduling information). In some examples, the number of bits may be determined and/or identified by a bit allocation module at the eRRH. The bit allocation module may determine that the number of bits used for each PUSCH I/Q symbol is four bits per symbol when the modulation order is quadrature phase shift keying (QPSK), five bits per symbol when the modulation order is 16-quadrature amplitude modulation (16-QAM), and six bits per symbol when the modulation order is 64-quadrature amplitude modulation (64-QAM).

As in 570, lossy compression can be performed at the UE. In some examples, lossy compression can be performed by a compression module at the eRRH. As part of the lossy compression (or as a preliminary pre-processing action), each PUSCH I/Q sample in a plurality of PUSCH I/Q samples corresponding to a plurality of PUSCH I/Q symbols (e.g., frequency domain I/Q samples generated by performing an FFT on the time domain I/Q samples corresponding to the PUSCH I/Q symbols) can be normalized. In some examples, each PUSCH I/Q can be normalized to a value in the range of -1 to 1 by subtracting a mean value and applying a scale value. The normalized PUSCH I/Q samples can then be quantized based on the number of bits. In some examples, uniform scalar quantization can be applied to each normalized PUSCH I/Q sample (e.g., by a uniform scalar quantizer).

As in 580, lossless compression can be performed at the UE. In some examples, lossless compression can be performed by a compression module at the eRRH. In the lossless compression, a prefix-free code can be applied to a plurality of bit subsets, each of the plurality of bit subsets being associated with a corresponding PUSCH I/Q sample from the plurality of PUSCH I/Q samples. In some examples, each of the plurality of bit subsets can include the two most significant bits (MSBs) of the PUSCH I/Q sample associated with the bit subset. In some examples, the prefix-free code can be a Huffman code in which an MSB value of 00 maps to a single coded bit having a value of 0; an MSB value of 01 maps to two coded bits having a value of 10; an MSB value of 10 maps to three coded bits having a value of 110; and an MSB value of 11 maps to four coded bits having a value of 111.

In some instances, the eRRH may also include a reference signal compression module configured to apply an additional compression technique (e.g., a compression technique different from the compression technique applied to bit subsets, I/Q samples, and/or PUSCH symbols) to at least one of a reference signal, a physical uplink control channel (PUCCH) symbol, or a random access channel (RACH) signal.

Figure 6 provides an example illustration of a wireless device such as a user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet computer, a mobile phone, or other type of wireless device. The wireless device may include one or more antennas configured to communicate with a node, macro node, low power node (LPN), or transmitting station such as a base station (BS), an evolved Node B (eNB), a baseband processing unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station (BS), a radio equipment (RE), or other type of wireless wide area network (WWAN) access point. The wireless device may be configured to communicate using at least one wireless communication standard, including 3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi. The wireless device may communicate using a separate antenna for each wireless communication standard or using a shared antenna for multiple wireless communication standards. The wireless device may communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

FIG6 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen can be a liquid crystal display (LCD) screen, or other types of display screens such as organic light emitting diode (OLED) displays. The display screen can be configured as a touch screen. The touch screen can use capacitive, resistive, or other types of touch screen technology. An application processor and a graphics processor can be coupled to internal memory to provide processing power and display capabilities. Non-volatile memory can also be used to provide data input/output options for the user. The non-volatile memory port can also be used to expand the storage capacity of the wireless device. A keyboard can be integrated with the wireless device or wirelessly connected to the wireless device to provide additional user input. The touch screen can also be used to provide a virtual keyboard.

Various technologies or some aspects or portions thereof may take the form of program code (i.e., instructions) contained in a tangible medium such as a floppy disk, CD-ROM, hard drive, permanent computer-readable storage medium, or any other machine-readable storage medium, wherein when the program code is loaded into a machine such as a computer and executed by it, the machine becomes an instrument for practicing various technologies. Circuit systems may include hardware, firmware, program code, executable code, computer instructions, and/or software. Permanent computer-readable storage media may be computer-readable storage media that does not include signals. When the program code is executed on a programmable computer, the computing device may include a processor, a storage medium readable by the processor (including volatile memory and non-volatile memory and/or storage element), at least one input device, and at least one output device. The volatile memory and non-volatile memory and/or storage element may be RAM, EPROM, flash memory, optical drive, hard drive, magnetic hard drive, solid-state drive, or other medium for storing electronic data. Nodes and wireless devices may also include transceiver modules, counting modules, processing modules, and/or clock modules or timer modules. One or more programs that can implement or utilize the various technologies described herein may use application programming interfaces (APIs), reusable controls, and the like. Such a program can be implemented in a high-level procedural language or an object-oriented programming language to communicate with a computer system. However, if desired, the program can be implemented in assembly language or machine language. In any case, the language can be compiled or interpreted and combined with hardware implementation.

As used herein, the term processor may include general purpose processors, special purpose processors such as VLSI, FPGA, and other types of special purpose processors, as well as baseband processors used to transmit, receive, and process wireless communications in a transceiver.

It should be understood that many of the functional units described in this specification are labeled as modules to more particularly emphasize their implementation independence. For example, a module can be implemented as a hardware circuit (e.g., an application-specific integrated circuit) including a custom VLSI circuit or gate array, an off-the-shelf semiconductor such as a logic chip, a transistor, or other discrete components. A module can also be implemented in a programmable hardware device such as a field programmable gate array, programmable array logic, a programmable logic device, or the like.

Modules may also be implemented by software executed by various types of processors. For example, an identified module of executable code may include one or more physical or logical blocks of computer instructions, which may be organized into objects, procedures, or functions, for example. Nevertheless, the executable files of an identified module need not be physically located together, but may include distinct instructions stored in different locations that, when logically combined together, constitute the module and achieve the specified purpose for the module.

In practice, a module of executable code can be a single instruction or many instructions, and can even be distributed across several different code segments, in different programs, and across several memory devices. Similarly, operational data can be identified and described within a module herein and can be implemented in any suitable form and organized within any suitable type of data structure. The operational data can be collected as a single data set or can be distributed across different locations, including on different storage devices, and can exist at least in part simply as electronic signals on a system or network. A module can be passive or active, including agents operable to perform a desired function.

As used herein, the term "processor" may include general-purpose processors, special-purpose processors such as VLSI, FPGA, and other types of special-purpose processors, as well as baseband processors used to transmit, receive, and process wireless communications in a transceiver.

The "example" mentioned throughout this specification means that a particular feature, structure, or characteristic described in conjunction with the example is included in at least one embodiment. Therefore, the phrase "in an example" appearing in various places throughout this specification is not necessarily all referring to the same embodiment.

As used herein, for convenience, multiple items, structural elements, constituent elements and/or materials may be presented in a common list. However, these lists should be interpreted as if each member of the list is individually identified as a separate and unique member. Therefore, in the absence of contrary instructions, the individual members of such lists should not be interpreted as actual equivalents of any other members of the unified list simply based on their presence in a common group. In addition, various embodiments and examples may be referred to herein together with alternatives to their various components. It should be understood that such embodiments, examples and alternatives should not be interpreted as actual equivalents of each other, but should be interpreted as separate and independently existing embodiments, examples and alternatives.

Furthermore, the described features, structures, or characteristics may be combined in any manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of layouts, distances, network examples, etc., to provide a thorough understanding of some embodiments. However, those skilled in the relevant art will recognize that some embodiments may differ with respect to one or more specific details, or with respect to other methods, components, layouts, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments.

While the above examples illustrate the principles of some embodiments in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made in form, use, and details of implementation without exercising inventive ability and without departing from the principles and concepts set forth in the present disclosure and claims. Accordingly, the present disclosure or drawings are not intended to be limiting; intended limitations are set forth in the following claims.

Claims (14)

1. An enhanced remote radio head (eRRH) configured for use in a cloud-based radio access network (C-RAN), wherein baseband physical layer processing is decoupled between a baseband processing unit (BBU) pool and the eRRH, the eRRH comprising: One or more processors; An analog front-end AFE, configured to receive radio signals from at least one user equipment (UE) via one or more antennas; An analog-to-digital converter (ADC) configured to receive the radio signal from the AFE and digitize the radio signal; Control/data splitter module, the control/data splitter module being configured to: Receive digitized radio signals from the ADC; The cyclic prefix removal of the digital radio signal is performed using one or more processors; and Identify multiple time-domain Physical Uplink Shared Channel (PUSCH) phase/orthogonal I/Q samples in the digital radio signal, wherein the multiple time-domain PUSCH I/Q samples correspond to multiple PUSCHI/Q symbols, and wherein the multiple PUSCHI/Q symbols are associated with a Physical Resource Block (PRB). A Fast Fourier Transform (FFT) module is configured to receive the plurality of time-domain PUSCH I/Q samples from the control/data separator module and perform a Fast Fourier Transform on the plurality of time-domain PUSCH I/Q samples to generate a plurality of frequency-domain PUSCH/Q samples corresponding to the plurality of PUSCH/Q symbols. Bit allocation module, the bit allocation module is configured as follows: User scheduling information is received from the BBU pool via the fronthaul link. This user scheduling information is associated with the PRB and includes one or more of the following: constellation or modulation for each subcarrier, Turbo coding rate, number of users scheduled in MIMO, Hybrid Automatic Repeat Request (HARQ) status, Target Signal-to-Interference-to-Noise Ratio (SINR), or average bit/block error performance; and Based on the user scheduling information, the number of bits to be allocated to each of the plurality of PUSCH I/Q symbols is identified; and Compression module, the compression module is configured to: Receive the plurality of frequency domain PUSCH I/Q samples from the FFT module; Receive from the bit allocation module the number of bits used for each PUSCH I/Q symbol among the plurality of PUSCH I/Q symbols; and Lossy compression is performed, in which each frequency domain PUSCH I/Q sample of the plurality of frequency domain PUSCH I/Q samples corresponding to the plurality of PUSCH I/Q symbols is normalized, and each frequency domain PUSCH I/Q sample is quantized based on the number of bits received from the bit allocation module. 2. The eRRH of claim 1, wherein the compression module is further configured to normalize each of the plurality of frequency domain PUSCH I/Q samples to a value in the range of -1 to 1 by subtracting the average value and using a scaling value. 3. The eRRH of claim 1, wherein the compression module is further configured to apply uniform quantization to quantize each of the plurality of frequency domain PUSCH I/Q samples. 4. The eRRH of claim 1, wherein the bit allocation module is further configured to identify the number of bits for each of the plurality of PUSCHI/Q symbols based on the modulation order contained in the user scheduling side information. 5. The eRRH according to claim 4, wherein the bit allocation module is further configured to determine: when the modulation order is quadrature phase shift keying (QPSK), the number of bits to be allocated to each PUSCH I/Q symbol is four bits per symbol; when the modulation order is 16 quadrature amplitude modulation (16-QAM), the number of bits is five bits per symbol; and when the modulation order is 64 quadrature amplitude modulation (64-QAM), the number of bits is six bits per symbol. 6. The eRRH of claim 1, wherein the compression module is further configured to perform lossless compression after performing lossy compression, wherein a prefixless code is applied to a plurality of bit subsets, each of the plurality of bit subsets being associated with a corresponding PUSCH I/Q sample in a plurality of quantized normalized PUSCH I/Q samples. 7. The eRRH of claim 6, wherein each of the plurality of bit subsets comprises the two most significant bits (MSB) of the corresponding frequency domain PUSCHI/Q sample in the plurality of frequency domain PUSCHI/Q samples. 8. The eRRH according to claim 7, using Huffman coding as the unprefixed code, wherein: The MSB value 00 is mapped to a single coded bit with a value of 0; The MSB value 01 is mapped to two coded bits with a value of 10; The MSB value 10 is mapped to three coded bits with a value of 110; and The value 11 of the MSB is mapped to four coded bits with the value 111. 9. The eRRH of claim 1, wherein the control/data splitter module is further configured to identify a reference signal, a Physical Uplink Control Channel (PUCCH) symbol, and a Random Access Channel (RACH) signal in the radio signal, and wherein the eRRH further includes a reference signal compression module configured to apply a compression technique different from that applied to the plurality of PUSCH symbols to at least one of the reference signal, the PUCCH symbol, or the RACH signal. 10. A computer-readable storage medium having one or more computer programs stored thereon, the one or more computer programs performing the following operations when executed by one or more processors: Receive radio signals at the enhanced remote radio head eRRH; Cyclic prefix removal is performed on the radio signal at the eRRH; Identify multiple time-domain Physical Uplink Shared Channel (PUSCH) phase/orthogonal I/Q samples in the radio signal, wherein the multiple time-domain PUSCH I/Q samples correspond to multiple PUSCH I/Q symbols, and wherein the multiple PUSCH I/Q symbols are associated with Physical Resource Blocks (PRBs) in the radio signal; At the eRRH, a fast Fourier transform is performed on the plurality of time-domain PUSCH I/Q samples to generate a plurality of frequency-domain PUSCH/Q samples corresponding to the plurality of PUSCH/Q symbols. At the eRRH, user scheduling side information is received from the BBU pool or the evolved Node B (eNB) via the fronthaul link. The user scheduling side information is associated with the PRB and includes one or more of the following: constellation or modulation for each subcarrier, Turbo coding rate, number of users scheduled in multiple-input multiple-output MIMO, hybrid automatic repeat request (HARQ) status, target signal-to-interference-to-noise ratio (SINR) or average bit/block error performance. At the eRRH, the specified number of bits to be used for each of the plurality of PUSCHI/Q symbols is identified based on the user scheduling side information; At the eRRH, each frequency domain PUSCHI/Q sample in the plurality of frequency domain PUSCHI/Q samples is normalized, the plurality of frequency domain PUSCHI/Q samples corresponding to the plurality of PUSCHI/Q symbols; and Lossy frequency domain compression is performed at the eRRH, in which each frequency domain PUSCHI/Q sample in the plurality of frequency domain PUSCHI I/Q samples is discretized based on the specified number of bits. 11. The computer-readable storage medium of claim 10, wherein the one or more computer programs, when executed by one or more processors, further perform the following operations: The specified number of bits to be used for each of the plurality of PUSCHI/Q symbols is identified based on the modulation order contained in the user scheduling side information. 12. The computer-readable storage medium of claim 10, wherein the one or more computer programs, when executed by one or more processors, further perform the following operations: Lossless compression is performed after lossy frequency domain compression, in which no-prefix code is applied to multiple bit subsets, each of which is associated with a corresponding frequency domain PUSCHI/Q sample in multiple discretized frequency domain PUSCHI/Q samples. 13. The computer-readable storage medium of claim 12, wherein each of the plurality of bit subsets includes the two most significant bits (MSB) of a corresponding PUSCH I/Q sample associated with the bit subset. 14. The computer-readable storage medium of claim 13, wherein the unprefixed code is Huffman code, wherein: The MSB value 00 is mapped to a single coded bit with a value of 0; The MSB value 01 is mapped to two coded bits with a value of 10; The MSB value 10 is mapped to three coded bits with a value of 110; and The value 11 of the MSB is mapped to four coded bits with the value 111.