Enabling Spectrum Sharing between LTE and RADAR Systems in S-Band

Radar interference into LTE base stations in the 3.5 GHz band

In order to coexist with the WiFi systems in the unlicensed spectrum, Long Term Evolution (LTE) networks can utilize periodically configured transmission gaps. In this paper, considering a time division duplex (TDD)-LTE system, we propose a Q-Learning based dynamic duty cycle selection technique for configuring LTE transmission gaps, so that a satisfactory throughput is maintained both for LTE and WiFi systems. By explicitly taking the impact of IEEE 802.11n beacon transmission mechanism into account, we evaluate the coexistence performance of WiFi and LTE using the proposed technique. Simulation results show that the proposed approach can enhance the overall capacity performance by 19% and WiFi capacity performance by 77%, hence enabling effective coexistence of LTE and WiFi systems in the unlicensed band.

Coexistence research for LTE systems is indispensable to ensure that the time division duplex (TDD) Long Term evolution (LTE) system can coexist with the frequency division duplex (FDD) LTE system operating at the adjacent frequency band within the same geographical area. Previous studies on this topic only focus on the throughput loss of the victim system from the data channel viewpoint. In this paper, the performance of control channels (CCHs) in the typical coexistence scenario is investigated, since the performance of communication systems is largely dependent on the quality of CCHs. The CCHs' interferences are analyzed in detail, including the coexistence issue for CCHs, Co-Channel Interference (CCI) analysis, and Adjacent Channel Interference (ACI) on CCHs. The simulation results indicate that the ACI generated by the Base Station (BS) of collocated LTE system degrades the performance of the uplink (UL) CCHs of the victim LTE system significantly.

The fifth-generation (5G) mobile network is facing severe challenges of the traffic demand surge and spectrum scarcity. To improve the network capacity and data rate, the deployment of Long Term Evolution (LTE) cellular system on unlicensed band is considered as one of the promising solutions. But the interference problem among LTE and WiFi system on the same unlicensed band hinders the deployment process, which is a critical issue unsolved for network operators. Therefore, a novel channel access scheme integrating the energy detection scheme and back-off mechanism in LTE system has been proposed in this paper, to minimize the interference to WiFi system. The throughput of both LTE and WiFi systems and the optimal sensing time and back-off time are theoretically analyzed with proofs. Furthermore, an efficient adaptive reconfiguration strategy of access parameters is proposed based on the channel occupancy cognition results. Simulation results verify that the proposed channel access scheme with optimal back-off time can double the throughput of WiFi system when coexisting with LTE system on unlicensed band.

Dynamic Spectrum Sharing (DSS) enables spectrum sharing between Long-Term Evolution (LTE) and New Radio (NR) systems, addressing spectrum scarcity in NR. To avoid interference when supporting NR traffic within LTE spectrum, key factors must be compatible. Effective DSS techniques are essential for coexistence. This paper discusses these issues in two parts. Part I covers LTE and NR coexistence using DSS, introducing resource grids, control signals, and channels, and explores DSS approaches for NR data traffic, including NR Synchronization Signal/Physical Broadcast Channels (SSB) transmission via LTE Multicast-Broadcast Single-Frequency Network (MBSFN) and non-MBSFN subframes with associated challenges and standardization efforts for DSS improvement. Part II presents a DSS technique using MBSFN subframes in a heterogeneous network with a macrocell and picocells running on LTE, and in-building small cells running on NR, sharing LTE spectrum via DSS. An optimization problem is formulated to manage traffic through MBSFN allocation, determining the optimal number of MBSFN subframes per LTE frame. System simulations indicate DSS improves Spectral and Energy Efficiency in small cells. The paper concludes with key lessons for LTE and NR coexistence.

In this paper, the truncated singular value decomposition expectation-maximization (TSVD-EM) based channel estimation on single transmit antenna transmission is extended to transmit diversity transmission. Particular attention is given to Long Term Evolution (LTE) systems. In order to obtain the received symbols for each transmit antenna, an approximation is proposed by using the soft symbols and channel estimates from the previous iteration. We prove that the mean square error (MSE) of TSVD-EM on transmit diversity transmission has almost the same constant value at high signal-to-noise ratio (SNR) as on single transmitter antenna case. Simulation results show that the proposed TSVD-EM channel estimation improves system performances remarkably and approaches the performance with perfect channel state information. Even without pilot boosting used in LTE systems, the TSVD-EM achieves the same performances as with pilot boosting.

The new radio (NR) system is recently proposed to deploy alongside the long term evolution (LTE) system to improve the wireless communication capacity. The Vandermonde-subspace frequency division multiplexing (VFDM) is an efficient technique for such a two tier network, whereby the NR transmitter can reuse the frequency spectrum of LTE system meanwhile guaranteeing interference free to LTE. In this paper, we first investigate the robust rate-maximization problem in the VFDM system. In the condition of imperfect channel state information (CSI), the precoder is optimized to satisfy both non-interference to LTE system and rate-maximization in the NR system. To tackle the challenge in solving such a non-convex problem, an iterative algorithm is proposed based on the block coordinate descent (BCD) and penalty dual decomposition (PDD) methods. Finally, simulation results demonstrate the superiority of the proposed algorithm in terms of robustness and achievable rate over the conventional SVD-based VFDM technique.

In order to satisfy the requirement of reliability in the TD-LTE RF Conformance Testing Instrument, a method to achieve the synchronization of protocol and physical layer based on embedded system is imposed. According to the feature of the long term evolution (LTE) system, it highlights the details to enhance the synchronization between various aspects in the LTE system through General-Purpose Memory Controller (GPMC) from ARM. GPMC is a memory controller that helps achieve the primitive interaction between the protocol and physical layer and the application. What is more important is that GPMC achieves the coordination that means LTE works at the same time in the same frame of the same sub-frame. Verified multiple times this design achieves the synchronization of aspects in LTE as well as meets the requirement of hardware platform in TD-LTE RF Conformance Testing Instrument.

Multiple input multiple output (MIMO) technique that requires multiple antennas at both transmitter and the receiver is a key technology to meet the peak data rates and spectral efficiency targets of long term evolution (LTE) systems. MIMO is a widely researched topic, and understanding of MIMO concepts have an interaction with other essential enhancement mechanisms in the system including link adaptation, resource scheduling, inter stream interference, rank of the channel, etc. This paper mainly aims to target the MIMO mode adaptation strategies in LTE systems by considering the rank and other key parameters like antenna correlation, doppler frequency, bit rate, throughput, etc. 3GPP LTE rel-8 has adopted seven MIMO modes and variable modulation and coding schemes (MCS) to effectively utilize the available resources for maximizing the throughput of the system. In this paper, new techniques for obtaining appropriate rank and a new MIMO mode switching algorithm to maximize data rate of the user equipment (UE) for a given channel consider at the receiver with reasonable complexity, and there by improving the average system throughput are proposed. The paper considers only four MIMO modes namely transmit diversity, open loop spatial multiplexing (OLSM), closed loop spatial multiplexing (CLSM) and beam-forming with different modulation levels. MIMO mode switching is done based on throughput value between open loop modes namely transmit diversity and OLSM for high mobility UE in the presence of co channel interference (CCI). Similarly, mode switching is done between closed loop modes namely CLSM and beam-forming for pedestrian UE in the presence of CCI. Simulation results are provided to illustrate the performance benefits of the proposed algorithm. The simulation results reveal that these new techniques improves the system throughput significantly.

For fifth generation (5G) communications, full-duplex radio is one of the key technologies to increase the spectral efficiency. To apply full duplex to commercial wireless communication systems, it is crucial to adopt effective self- interference cancellation (SIC) techniques, which are compatible with the standards. In this paper, we focus on applying full duplex to the current long term evolution (LTE) standard. We introduce three LTE-compatible SIC methods and these are investigated in terms of reference signal, SIC performance, and stability. Numerical results confirm that, in certain conditions, full duplex can be applied and improve LTE systems especially in small-cell environments.

The 3GPP Long Term Evolution (LTE) Release-8 specifications are designed to deliver higher peak data rates, higher throughput and lower air-interface latency compared to 2G and 3G systems. This higher performance will make it possible to support more demanding applications beyond web-browsing and voice, requiring higher data rates and stricter QoS constraints. Video services are becoming increasingly popular over the Internet indicating that the demand for such high data-rate video applications over cellular wireless will continue to grow. However, in order to make these services commercially viable in a LTE system it is necessary for the air-interface to deliver high quality services to a significant number of users simultaneously. In this paper we investigate the video capacity of a LTE air-interface using realistic video traffic models. An LTE air-interface can support multiple-antenna transmit arrays and several multiple antenna transmission modes to increase system capacity. We investigate the benefits of using 4 transmit antennas compared to 2 transmit antennas on the video capacity of an LTE system. The results from our investigation indicate that the capacity benefits with 4 transmit antennas are much higher with video services than those observed with other traffic models such as the full-buffer traffic model. The results also show that a 10MHz TDD LTE system can service upto 48 users per sector with 256Kbps video streams in the downlink indicating that such services can be commercially viable.

Recently, vehicular communication has become an important application in wireless communications. The Long Term Evolution (LTE) system is considered as one candidate to realize vehicular communication due to many reasons, such as: 1. The LTE system provides extensive coverage. 2. The LTE system provides low transmission latency. 3. In Release 12, the LTE system supports ProSe device-todevice (D2D) service, which can be extended to support vehicular communication.

With the soaring demands for high speed data communication, as well as transmission of various types of services with different requirements over cellular networks, having a decent radio resource management is considered vital in Long Term Evolution (LTE) system. In particular, satisfying the quality of service (QoS) requirements of different applications is one of the key challenges of radio resource management that needs to be dealt by the LTE system. In this paper, we propose a cross-layer design scheme that jointly optimizes three different layers of wireless protocol stack, namely application, Medium Access Control, and physical layer. The cross-layer optimization framework provides efficient allocation of wireless resources across different types of applications (i.e., real-time and non real-time) run by different users to maximize network resource utilization and user-perceived QoS, or also known as Quality of Experience (QoE). Here, Mean Opinion Score is used as a unified QoE metric that indicates the user-perceived quality for real-time or multimedia services notably video applications. Along with multimedia services, the proposed framework also takes care of non-real-time traffic by ensuring certain level of fairness. Our simulation, applied to scenarios where users simultaneously run different types of applications, confirms that the proposed QoE-oriented cross-layer framework leads to significant improvement in terms of maximizing user-perceived quality as well as maintaining fairness among users.

Multi-input-multi-output (MIMO) systems along with orthogonal frequency division multiplexing (OFDM) technique plays a crucial role in 4G based wireless networks. The inclusion of MIMO technology enables new types of links such as downlink multi-user communication. Long term evolution (LTE) systems are based on multi-user MIMO technologies, which have flexible bandwidths. In this paper, we derived closed form expression of bit error rate (BER) for multi-user LTE and LTE-Advanced (LTE-A) systems. Moment generating function (MGF) and pair-wise error probability (PEP) based approaches are used to derive these BER expressions. Theoretical results of BER are validated using simulation results for different number of users. Results are plotted on the basis of various features such as coordinated multipoint (CoMP) transmission and reception, multimedia broadcast and multicast services (MBMS) and allocation of Bandwidth in LTE and LTE-A systems.

In the current environment of burgeoning demand for mobile broadband, Long Term Evolution (LTE) is the most preferred wireless technology for the mobile operators. Considering the legacy multi-technology networks, operators need to strategically work upon maximizing their revenue while minimizing their cost and satisfying the subscriber’s requirements as well. Operators have a choice between 2 network strategies- LTE overlay and single radio access network (SRAN). A survey carried out proved SRAN to be the optimum LTE deployment strategy considering the total cost of ownership (TCO). This paper discusses the effect on the system performance due to the up gradation of network from second generation (2G) to third generation (3G) to long term evolution (LTE) systems using Nokia Siemens Network Flexi multi-radio base stations. Measurements of RSRP (Reference Signal Received Power), SINR (Signal to Interference plus Noise Ratio) and throughput were carried out by a drive test within 2Km of the deployed site area which indicated that all the 3 parameters were affected as the user equipment moved away from the site area and towards the cell edges. This problem can be addressed by deployment of low power relay nodes, one of the promising techniques, for increasing the coverage of LTE advanced networks (the future of LTE systems).