Base Station Equipment Research Articles

Compressive Sensing (CS) Assisted Low-Complexity Beamspace Hybrid Precoding for Millimeter-Wave MIMO Systems

Hybrid analog/digital precoding is a promising technique to reduce the hardware cost of radio-frequency components compared with the conventional full-digital precoding approach in millimeter-wave multiple-input multiple output systems. However, the large antenna dimensions of the hybrid precoder design makes it difficult to acquire an optimal full-digital precoder. Moreover, it also requires matrix inversion, which leads to high complexity in the hybrid precoder design. In this paper, we propose a low-complexity optimal full-digital precoder acquisition algorithm, named beamspace singular value decomposition (SVD) that saves power for the base station and user equipment. We exploit reduced-dimension beamspace channel state information (CSI) given by compressive sensing (CS) based channel estimators. Then, we propose a CS-assisted beamspace hybrid precoding (CS-BHP) algorithm that leverages CS-based CSI. Simulation results show that the proposed beamspace-SVD reduces complexity by 99.4% compared with an optimal full-digital precoder acquisition using full-dimension SVD. Furthermore, the proposed CS-BHP reduces the complexity of the state-of-the-art approach by 99.6% and has less than 5% performance loss compared with an optimal full-digital precoder.

Coverage and Link Quality Trends in Suburban Mobile Broadband HSPA Network Environments

Radio coverage shrinkage is one of the key factors that places limitation on link data transmission rate quality in mobile broadband networks, especially on users at cell edge. This occurs due to multipath radio signal fading, frequent changes in radio propagation conditions and base station equipment deterioration. Other key limiting factors includes intercellular/intracellular interference and random background noise in the network environment. Within this context, the importance of carrying out a routine independent assessments of deployed mobile communication networks in a realistic environment has also increased. This is to evaluate their robustness and performance capability in different radio propagation scenarios from one location to the other. This research work deals with practical performance monitoring and evaluation of deployed commercial mobile broadband HSPA networks, considering the radio coverage and service quality aspects in typical suburban environments. The aim is to correlate cell coverage with radio link quality performance indicators in different propagation environments. The aim have been accomplished by carrying out field test measurement campaign and a drill down post data analysis on the HSPA networks and this enable us to critically examined and relate vital QoS parameters at the cell site specific level. Finally, based on Block Error rate performance threshold, the cell radius has been estimated for each measurement routes. The results could form the basis for performance optimisation of mobile cellular networks.

MIMO AF RSs Based OSTBCs for LTE-A Downlink Physical Layer Network

The link performance between base station (BS) and user equipment (UE) in long term evolution-advanced (LTE-A) system is already quite close to the Shannon limits and from a pure link-budget perspective, the highest data rates supported by LTE-A require a relatively high signal-to-noise ratio. In later releases of LTE-A, various tools such as relaying, enhancing the support for low-power BSs and improving the link budget are included. This paper studies the relay stations (RSs) for LTE-A downlink physical layer. Multi-input multi-output amplify-and-forward RS is used to enhance the received signal of UEs at cell edge. This paper proposes RSs with orthogonal space–time block codes (OSTBC) transmission for LTE-A system. The received signals for different UEs scenarios are mathematically derived and analyzed. The symbol error rate performance of proposed LTE-A system is illustrated for the scenarios of UEs. Results show that the proposed LTE-A system based RSs with OSTBC transmission improve link performance and achieve higher diversity gains.

Energy and Traffic Aware Full-Duplex Communications for 5G Systems

In this paper, we consider the problem of resource allocation in a dense small-cell network. Each small-cell base station is powered by a renewable energy source and operates in the full-duplex mode. We account for the rate-dependent energy term for data decoding into the total energy consumption at the small-cell base station. Owing to this new energy term, the transmitter and receiver operations now draw the energy from a common source. For a new energy consumption model and high interference scenario, which arises due to full-duplex communications, we formulate an energy and load aware resource management optimization problem under the energy causality and total transmit power constraints of the small-cell base station and uplink user equipments. In particular, the problem minimizes the data queue length of each network user equipment by jointly designing the beamformers, power, and sub-carrier allocation and their scheduling. Owing to the non-convexity of the problem, a global solution is inefficient; thus, we opt for the successive parametric convex approximation method to obtain a sub-optimal solution. This method solves for the convex approximate of the non-convex problem in each iteration and leads to faster convergence. For practical implementation, we further develop a distributed algorithm by using the dual decomposition framework, which relies on limited exchange of information between the involved base stations. Numerical simulations compare the network scenario which accounts for uplink channel rate-dependent energy consumption with that which ignores it. Results advocate the need for redesigning of the resource allocation scheme. In addition, numerical simulations also validate the usefulness of full-duplex communications over the half-duplex communications in terms of minimizing the sum data queue length of the users.

Millimeter-Wave Transmission for Small-Cell Backhaul in Dense Urban Environment: a Solution Based on MIMO-OFDM and Space-Time Shift Keying (STSK)

Next generation wireless standards will exploit the wide bandwidth available at the millimeter-wave (mm-Wave) frequencies, in particular the $E$ -band (71–76 and 81–86 GHz). This large available bandwidth may be converted into multi-gigabit capacity, when efficient and computationally affordable transceivers are designed to cope with the constrained power budget, the clustered fading, and the high level of phase noise, which actually characterize mm-wave connections. In this paper, we propose a viable multiple-input multiple-output (MIMO) solution for high bit-rate transmission in the $E$ -band with application to small-cell backhaul based on space-time shift keying (STSK) and orthogonal frequency division multiplexing. STSK provides an efficient tradeoff between diversity and multiplexing without inter-channel interference and without the need for large antenna arrays. These features make STSK theoretically preferable over other throughput-oriented space-time coding techniques, namely, spatial multiplexing and spatial modulation, which were recently considered in the literature for mm-wave MIMO applications. In this paper, we consider the most significant channel impairments related to small-cell backhaul in dense urban environment, namely, the correlated fading with and without the presence the line-of-sight, the phase noise, the rain attenuation, and shadowing. In addition, we consider small-size MIMO systems ( $2 \times 2$ and $4 \times 4$ ), and low-cost base station equipments in the perspective of easily deployable small-cell network components. Comparative results, obtained by intensive simulations targeted at assessing link performance and coverage, have clearly shown the superior performance of STSK against counterpart techniques, although obtained at the cost of a somewhat reduced spectral efficiency.

Incentive and Architecture of Multi-Band Enabled Small Cell and UE for Up-/Down-Link and Control-/User-Plane Splitting for 5G Mobile Networks

Abstract In this paper, a multi-band enabled femtocell base station (FCBS) and user equipment (UE) architecture is proposed in a multi-tier network that consists of small cells, including femtocells and picocells deployed over the coverage of a macrocell for splitting uplink and downlink (UL/DL) as well as control-plane and user-plane (C-/U-plane) for 5G mobile networks. Since splitting is performed at the same FCBS, we define this architecture as the same base station based split architecture (SBSA). For multiple bands, we consider co-channel (CC) microwave and different frequency (DF) 60 GHz millimeter wave (mmWave) bands for FCBSs and UEs with respect to the microwave band used by their over-laid macrocell base station. All femtocells are assumed to be deployed in a 3-dimensional multi-storage building. For CC microwave band, cross-tier CC interference of femtocells with macrocell is avoided using almost blank subframe based enhanced inter-cell interference coordination techniques. The co-existence of CC microwave and DF mmWave bands for SBSA on the same FCBS and UE is first studied to show their performance disparities in terms of system capacity and spectral efficiency in order to provide incentives for employing multiple bands at the same FCBS and UE and identify a suitable band for routing decoupled UL/DL or C-/U-plane traffic. We then present a number of disruptive architectural design alternatives of multi-band enabled SBSA for 5G mobile networks for UL/DL and C-/U-plane splitting, including a disruptive and complete splitting of UL/DL and C-/U-plane as well as a combined UL/DL and C-/U-plane splitting, by exploiting dual connectivity on CC microwave and DF mmWave bands. The outperformances of SBSA in terms of system level capacity, average spectral efficiency, energy efficiency, and control-plane overhead traffic capacity in comparison with different base stations based split architecture (DBSA) are shown. Finally, a number of technical and business perspectives as well as key research issues of SBSA are discussed.

IEEE 802.22 passive radars: multistatic detection and velocity profiler

This work focuses on a passive coherent location (PCL) system that exploits the signals emitted by IEEE 802.22 devices, referred hereafter as a white-space PCL (WS-PCL) system. To cope with the very low transmitted equivalent isotropically radiated power of the IEEE 802.22 emitters, we focus on the design of a WS-PCL system that exploits all the useful signals, emitted from both the base station and customer-premises equipment, received in each frame. In this work, we study the feasibility of a WS-PCL system by deriving the receiver operating characteristic and defining the multistatic velocity profiling algorithm for the estimation of the target velocity vector. The performance of the proposed receiver is compared to that of a WS-PCL system that exploits only the signal emitted by the base station.

Time synchronization in communication networks based on the Beidou foundation enhancement system

Communication networks rely on time synchronization information generated by base station equipment (either the Global Navigation Satellite System receiver or rubidium atomic clock) to enable wireless networking and communications. Meanwhile, the time synchronization among base stations depends on the Network Time Protocol. With the development of mobile communication systems, the corresponding time synchronization accuracy has increased as well. In this case, the use of sparsely distributed-high-precision synchronization points to synchronize time for an entire network with high precision is a key problem and is the foundation of the enhanced network communication. The current receiver equipment for China’s digital synchronous network typically includes dedicated multi-channel GPS receivers for communication; however, with the development of GPS by the USA, network security has been destabilized and reliability is low. Nonetheless, network time synchronization based on Beidou satellite navigation system timing devices is an inevitable development trend for China’s digital communications network with the establishment of the independently developed BDS, especially the implementation and improvement of the Beidou foundation enhancement system.

Dynamic Access and Power Control Scheme for Interference Mitigation in Femtocell Networks

The femtocell network, which is designed for low power transmission and consists of consumer installed small base stations, coexists with macrocells to exploit spatial reuse gain. For its realization, cross-tier interference mitigation is an important issue. To solve this problem, we propose a joint access and power control scheme that requires limited information exchange between the femto and macro networks. Our objective is to maximize the network throughput while satisfying each users quality of service (QoS) requirement. To accomplish this, we first introduce two distributed interference detection schemes, i.e., the femto base station and macro user equipment based schemes. Then, the proposed scheme dynamically adjusts the transmission power and makes a decision on the access mode of each femto base station. Through extensive simulations, we show that the proposed scheme outperforms earlier works in terms of the throughput and outage probability.

Linear Multi-hop Amplify-and-Forward (AF) Cooperative Relay Channels

Cooperative relaying of channels between base station and user equipment emerged as a great technique to enhance the reliability and throughput of cellular networks. The relay nodes normally exploit amplify-and-forward (AF) scheme to relay the connection. Although there have been many previous works on cooperative issues, none of them have considered the fundamental trade-off between the communication reliability and transmission rate. Instead of considering the performance evaluated separately on the achievable rate or the error probability, the RCEE provide insight into fundamental trade-off between the transmission rate and the communication reliability in cooperative relay channels. It has been shown that multi-hop relay nodes are necessary to compensate the decreasing SNR over the distance. As a trade-off, the communication reliability in terms of RCEE is decreasing over the increase of multi-hop relay nodes with low SNR for a given data rate. Therefore, the optimization for the number of hops is preferable in the cooperative relay channels.Cooperative relaying of channels between base station and user equipment emerged as a great technique to enhance the reliability and throughput of cellular networks. The relay nodes normally exploit amplify-and-forward (AF) scheme to relay the connection. Although there have been many previous works on cooperative issues, none of them have considered the fundamental trade-off between the communication reliability and transmission rate. Instead of considering the performance evaluated separately on the achievable rate or the error probability, the RCEE provide insight into fundamental trade-off between the transmission rate and the communication reliability in cooperative relay channels. It has been shown that multi-hop relay nodes are necessary to compensate the decreasing SNR over the distance. As a trade-off, the communication reliability in terms of RCEE is decreasing over the increase of multi-hop relay nodes with low SNR for a given data rate. Therefore, the optimization for the number of hops is preferable in the cooperative relay channels.

Power Level Distributions of Radio Base Station Equipment and User Devices in a 3G Mobile Communication Network in India and the Impact on Assessments of Realistic RF EMF Exposure

The aim of this paper is to present results on output power level distributions of radio base stations (RBSs) and user devices connected to a wideband code division multiple access-based third generation (3G) mobile communication network in India and relate the results to realistic human exposure to radio frequency (RF) electromagnetic field (EMF) emitted by the corresponding RBSs and the devices. The output power level distributions have been obtained through network-based measurements. In downlink, data from 868 RBSs were gathered during seven days. The RBSs were connected to five different radio network controllers (RNCs) located in different regions of India. The mean, the median, and the 95th percentile RBS output power values were found to be 24%, 21%, and 53%, respectively, of the maximum available power. In the uplink direction, output power levels of 3G devices connected to 1256 RBSs and the same five RNCs as in the downlink were assessed separately for voice, data, voice + data, and video applications. In total, more than 1 million hours of data traffic and more than 700 000 h of voice calls were measured in the uplink. The mean output power for the voice, data, the voice + data, and the video were found to be around 1%, 3%, 2%, and 4%, respectively, of the maximum available power for the 3G user devices. The findings are in line with previously published results obtained in other networks in Europe, and demonstrate that knowledge on realistic power levels is important for accurate assessments of the RF EMF exposure.

A Large-Scale MIMO Precoding Algorithm Based on Iterative Interference Alignment

Abstract The performance of Large-scale MIMO system is degraded by Pilot Contamination. In order to reduce Pilot Contamination, a downlink precoding algorithm is put forward, based on Interference Alignment (IA). The main idea of this algorithm is aligning the pilot contamination and inter-cell interference to the same null space in order to acquire the maximal degrees of freedom. Then the downlink receiving precoding matrix is solved with respect to a maximal SINR (Signal Interference Noise Ratio) criterion. Exploiting the channel reciprocity and an iterative process, Base station and User Equipment switch transmitting and receiving roles in the uplink and downlink, the precoding matrices of the Base station and User Equipment is gradually updated until convergence. Finally, the simulation results have shown that the algorithm proposed can efficiently mitigate the impact of pilot contamination and outperform some popular precoding algorithms, e.g., MF precoding algorithm and MMSE precoding algorithm. When the number of antennas increases, the performance of the proposed algorithm will be greatly improved.

Remote Inspection System Algorithm Research of Wireless Base Station

In this paper, we apply the technology of Internet of things in wireless base station inspection. This actualize the long distance information acquisition about base station equipment and environment, actualize the real time feedback about hitch and alarm of station equipment, and improve stabilization of communication system and efficiency of inspections. A new remote control method based on SMS interception is proposed aiming at the problem that remote control must be connected to internet. Also a new anti-collision algorithm for simple labeling system is introduced aiming at the problem of multi-tag RFID conflicts. Finally, users can realize the remote control and inspection as long as they connect with internet.

IMPLEMENTATION OF TRANSMITTER AND RECEIVER ARCHITECTURE FOR PHYSICAL HYBRID INDICATOR CHANNEL OF LTE-ADVANCED USING PARTIAL RECONFIGURATION IN ML605 VIRTEX-6 DEVICE

LTE-A (Long Term Evolution-Advanced) is the fourth generation technology to increase the speed of wireless data network. The LTE-A Physical layer provides both data and control information between an enhanced base station and mobile user equipment which is quite complex and consists of a mixture of technologies. Since there is requirement for more resources to accommodate all the channels in a single FPGA, Partial Reconfiguration (PR) technique is introduced to configure the total hardware into sub modules that configure and operate in different instants of time. PR enables a part of FPGA to be reconfigured, while the rest continues to function without any interruptions and reduces the hardware resource power and fabric area. This work proposes the realization of transmitter and receiver architecture of Physical Hybrid Indicator Channel (PHICH) channel for LTE-A using partial reconfiguration on xc6vlx240tff1156-1 FPGA. The receiver architecture for PHICH is to report the correct reception of uplink user data to the User Equipment (UE) in the form of Acknowledgment (ACK), or Negative ACK (NACK) in a 1 millisecond duration sub-frame of Long Term Evolution (LTE) System. The modules for the different diversities are reconfigured based on the control signals from the transmitter.

Enabling LTE in TVWS with radio environment maps: From an architecture design towards a system level prototype

This paper reports recent prototyping efforts that show the feasibility of the radio environmental map to enable efficient exploitation of TV white spaces by a cellular LTE system. We describe a flexible REM backend implementation, fully integrated with standard-compliant operational LTE base station equipment. Simulations results indicate that REMs enhance white-space detection by their means to incorporate accurate and local channel propagation information, while experimental laboratory results illustrate the feasibility and performance of transmitter localization capabilities in a REM.

Experience of infrastructure damage caused by the Great East Japan Earthquake and countermeasures against future disasters

The Great East Japan Earthquake on March 11, 2011, which was the fourth strongest earthquake ever recorded in the world's history, severely damaged telecommunication facilities in unprecedented ways. The large-scale earthquake and tsunami affected many exchange office buildings and facilities. Further damage to services was caused due to the depletion of batteries associated with the prolonged disruption of the commercial power supply. The tremendous disaster caused service disruption to the communications infrastructure; in the case of NTT's facilities, approximately 1.5 million circuits for fixed lines and 4900 mobile base stations stopped working due to direct damage by the earthquake and/or tsunami or subsequent blackouts. However, more than 90 percent of the affected exchange offices and mobile base station equipment was restored by the end of March through an all-out effort by over 11,000 people. Even by the end of April, in areas where customers currently reside, service restoration has mostly been completed except for some areas experiencing construction difficulties, including damaged roads which made it difficult for workers to approach the site. In parallel with the restoration effort, a disaster emergency message service for voice, mobile, and the Internet was quickly provided in order to permit safety confirmation. The NTT Group installed temporary public telephones and Internet access environments, and also lent mobile phones, satellite mobile phones, and tablets free of charge to the affected people and government agencies. Since communication services are vital in modern society, we are making every effort to implement better countermeasures with future disasters in mind.

Radio Interface Evolution Towards 5G and Enhanced Local Area Communications

The exponential growth of mobile data in macronetworks has driven the evolution of communications systems toward spectrally efficient, energy efficient, and fast local area communications. It is a well-known fact that the best way to increase capacity in a unit area is to introduce smaller cells. Local area communications are currently mainly driven by the IEEE 802.11 WLAN family being cheap and energy efficient with a low number of users per access point. For the future high user density scenarios, following the 802.11 HEW study group, the 802.11ax project has been initiated to improve the WLAN system performance. The 3GPP LTE-advanced (LTE-A) also includes new methods for pico and femto cell's interference management functionalities for small cell communications. The main problem with LTE-A is, however, that the physical layer numerology is still optimized for macrocells and not for local area communications. Furthermore, the overall complexity and the overheads of the control plane and reference symbols are too large for spectrally and energy efficient local area communications. In this paper, we provide first an overview of WLAN 802.11ac and LTE/LTE-A, discuss the pros and cons of both technology areas, and then derive a new flexible TDD-based radio interface parametrization for 5G local area communications combining the best practices of both WiFi and LTE-A technologies. We justify the system design based on local area propagation characteristics and expected traffic distributions and derive targets for future local area concepts. We concentrate on initial physical layer design and discuss how it maps to higher layer improvements. This paper shows that the new design can significantly reduce the latency of the system, and offer increased sleeping opportunities on both base station and user equipment sides leading to enhanced power savings. In addition, through careful design of the control overhead, we are able to improve the channel utilization when compared with LTE-A.

Advanced Antenna Technologies in the Beyond IMT-Advanced Systems

[Extract] Both the fourth generation (4G) and fifth generation (5G) mobile systems will use multiple-input multiple-output(MIMO) technologies with multi antenna capabilities at both the base station and user equipment. To improve the capacity, extend the coverage, and decrease the antenna deployment complexity, many advanced antenna technologies have been proposed recently, such as the large-scale array antenna and the small-scale smart antenna. The large-scale array antenna system, also known as massive MIMO or massive three-dimension (3D) antenna, is a new research field in antenna systems, electronics, communication theory, and embedded software. It is often utilized in the frequency division duplex-(FDD-) based 4G & 5G systems, and its performance gain over the classical array antenna, which uses a relatively small number of antennas fed via coaxial cables from a high-power amplifier, is thus significant. However, one of the disadvantages of massive MIMO systems is that the antenna size is too large, resulting in a large frontal area. Meanwhile, the miniaturization of smart antenna (also known as the small-scale smart antenna) is often designed for the time division duplex (TDD) 4G & 5G systems and can effectively decrease the antenna size, while ensuring the capacity and coverage performances.

The unified UE baseband modem hardware platform architecture for 3GPP specifications

This paper presents the unified user equipment (UE) baseband modulation and demodulation (modem) hardware platform architecture to support multiple radio access technologies. In particular, this platform selectively supports two systems; one is HEDGE system, which is the combination of third generation partnership project (3GPP) Release 7 high speed packet access evolution (HSPA+) and global system for mobile communication (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE), while the other is LEDGE system, which is the combination of 3GPP Release 8 long term evolution (LTE) and GSM/GPRS/EDGE. This is done by applying the flexible pin multiplexing scheme to a hardwired pin mapping process. On the other hand, to provide stable connection, high portability, and high debugging ability, the stacking structure is employed. Here, a layered board architecture grouped by functional classifications is applied instead of the conventional one flatten board. Based on this proposed configuration, we provide a framework for the verification step in wireless cellular communications. Also, modem function/scenario test and inter-operability test with various base station equipments are verified by system requirements and scenarios.

Impact of Base Station Cooperation on Cell Planning

Base station cooperation (BSC) has been identified as a key radio access technology for next-generation cellular networks such as LTE-Advanced. BSC impacts cell planning, which is the methodical selection of base station (BS) sites, and BS equipment configuration for cost-effective cellular networks. In this paper, the impact of BSC on cell plan parameters (coverage, traffic, handover, and cost), as well as additional cell planning steps required for BSC are discussed. Results show that BSC maximizes its gains over noncooperation (NC) in a network wherein interference from cooperating BSs is the main limitation. Locations exist where NC may produce higher throughputs, therefore dynamic or semistatic switching between BSC and NC, called fractional BSC, is recommended. Because of interference from noncooperating BSs, the gains of BSC over NC are upper bounded, and diminishes at greater intersite distances because of noise. This encourages smaller cell sizes, higher transmit powers, and dynamic clustering of cooperative BSs.