Window-based frequency-domain packet scheduling with QoS support in LTE uplink

With the increase of the cell loadings, the interference among the adjacent cells becomes severer acting as the limiting factor for the cell-edge user performance. In this regard, there have been many standard activities in 3GPP (3rd Generation Partnership Project) to mitigate the ICI (Inter-Cell Interference). The eNB (Enhanced Node-B)-centric ICI mitigation having its own limit, the recent approaches incorporate the interference cancellation of a dominant interference from the adjacent cell at the receiver. However, for the LTE (Long Term Evolution) uplink, the SC-FDMA (Single-Carrier Frequency Division Multiple Access) structure prohibited the eNB to use a similar interference cancellation scheme as for the OFDMA (Orthogonal Frequency Division Multiple Access) UE (User Equipment) receiver. In this paper, we propose a blind interference cancellation receiver for LTE eNB, which performs ICI cancellation blindly without prior information of the adjacent cell interferences. It is shown that the proposed blind interference cancellation receiver for SC-FDMA provides significant performance gain against the conventional receiver.

In this paper, Collaborative MIMO is introduced to the Uplink of the Long Term Evolution (LTE) system. This technique uses two or more single carrier frequency division multiple access based user equipments (UEs) equipped with single antenna. These UEs transmit their data collaboratively over the same Resource block (RB), and then the Evolved Node B (eNodeB) separates the users' data by means of multiuser frequency domain equalization. This will increase the whole throughput of the LTE Uplink, besides moving the complexity of implementing multiple antennas to the eNodeB. In order to decode the data ZF, MMSE and successive interference cancellation (SIC) are employed although they didn't exploit the full spatial diversity, whereas the standard ML is abandoned for its exponential complexity. In this paper, we propose a novel Initial Guess based ML (IGML) receiver whose complexity is in the same order of ML receiver of OFDM-MIMO systems, and a QR based simplified ML receiver. We also propose two ordering techniques for the SIC receiver when used in shadowing environment, as well as various simulation parameters are examined to find the best collaborating environments. The simulation results reveal that the IGML receiver is far by almost 4.5dB at target BER of 10-4 from the traditional MMSE receiver.

Single Carrier Frequency Division Multiple Access (SC-FDMA) has been selected for use in the Long Term Evolution (LTE) uplink due to its lower Peak-to-Average Power Ratio (PAPR) relative to OFDMA The resultant lower PAPR results in fewer excursions into the amplifier's nonlinear region, where signal distortion can occur and results in degraded bit error rate (BER). The SC-FDMA scheme normally applies 16-ary Quadrature Amplitude Modulation (16-QAM), but amplitude phase shift keying (APSK) modulation has a lower PAPR than does 16-QAM, resulting in improved BER This paper investigates the constellation ring ratio of the 16-APSK modulation scheme and its effects on BER through its effects on the PAPR. Simulation results are used to conclude that a ring ratio that ranges from 2.5 to 3.5 delivers the best results and provides BER and PAPR improvement.

The Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard is becoming the appropriate choice to pave the way for the next generation wireless and cellular standards. While the popular OFDM technique has been adopted and implemented in previous standards and also in the LTE downlink, it suffers from high peak-to-average-power ratio (PAPR). High PAPR requires more sophisticated power amplifiers (PAs) in the handsets and would result in lower efficiency PAs. In order to combat such effects, the LTE uplink choice of transmission is the novel Single Carrier Frequency Division Multiple Access (SC-FDMA) scheme which has lower PAPR due to its inherent signal structure. While reducing the PAPR, the SC-FDMA requires a more complicated detector structure in the base station for multi-antenna and multi-user scenarios. Since the multi-antenna and multi-user scenarios are critical parts of the LTE standard to deliver high performance and data rate, it is important to design novel architectures to ensure high reliability and data rate in the receiver. In this paper, we propose a flexible architecture of a high data rate LTE uplink receiver with multiple receive antennas and implemented a single FPGA prototype of this architecture. The architecture is verified on the WARPLab (a software defined radio platform based on Rice Wireless Open-access Research Platform) and tested in the real over-the-air indoor channel.

This paper proposes a phase shift scheme in cyclic delay diversity (CDD) for single-carrier frequency division multiple access (SC-FDMA) in Internet of Things (IoT) applications. The proposed scheme is assumed to be applied to the uplink of Long Term Evolution (LTE) systems. Since the transmission rates of IoT applications are small, each uplink connection may occupy less than 12 subcarriers that corresponds to one resource block (RB) of the LTE. Since the length of the data sequence in time domain is short so that CDD may provide limited frequency diversity. The proposed scheme shifts the phases of the data symbols in time domain and spreads each subcarrier component over multiple subcarriers. Thus, more diversity gain can be realized with CDD. Numerical results obtained through computer simulation shows that the proposed scheme improves the performance by about 5 – 7 dB at the bit error rate (BER) of 104 for the data sequence length of 4.

The Long Term Evolution (LTE) standards are generated by the Third Generation Partnership Project (3GPP) for the Fourth Generation (4G) wireless communication systems. The Fourth Generation (4G) wireless communication standards use new physical layer signaling techniques in their physical layer. Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) are the two major signaling techniques used in LTE. OFDMA is used in the downlink of the Fourth Generation (4G) wireless communication systems for its high spectral efficiency and SC-FDMA is used in the uplink of the Fourth Generation (4G) wireless communication systems for its high power efficiency. The main objective of this paper is to design and implement the reliable and energy efficient architecture for LTE uplink system using FPGA. IFDMA is the most energy efficient subcarrier mapping scheme of SC-FDMA multiple access scheme. In IFDMA, the data symbols subcarrier mapping is not one to one instead each subcarrier carries a part from each data symbol transmitted at that time instant. The reason for the selection of IFDMA subcarrier mapping along with SC-FDMA multiple access scheme for LTE uplink comes mainly from its advantage to provide a low peak to average power ratio (PAPR) for the transmitted waveform. This results in less power consumption in the mobile station during uplink transmission. The reliability of the system is improved using interleaving process by avoiding packet loss. Convolution codes are less complex and are used to provide error free transmission. The enhancement of energy efficiency is done using the convolution coded IFDMA. The chosen energy efficient architecture must be more power efficient and support high data rates, which is the main requirement for the mobile user. The proposed reliable and energy efficient architecture for LTE uplink system is implemented using Xilinx system generator tool.

Joint user grouping and frequency allocation for multiuser SC-FDMA transmission

We consider the allocation of spectral and power resources every subframe (1~ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be a function of the sub-band. Moreover, the channel gains from the base-station to the mobiles (user equipment (UE) in LTE) can vary with the sub-band. The power and spectral resources are to be allocated among different UEs in a cell based on channel conditions, desired fairness/QoS, and constraints on power due to interference and power limitation at a UE. For $N$ UEs and $M$ sub-bands, we exploit the structure of the underlying optimization problem to obtain an $O(NM)$ algorithm for optimal resource allocation when a UE can be allocated resources in a non-contiguous manner in frequency. To implement this in an OFDMA system, we delineate a simple control signalling structure where the UE computes in $O(M)$ time a waterfilling solution every subframe it is assigned resources. When the allocation is restricted to contiguous allocation in frequency due to single carrier constraint in LTE, we convert the solution computed above in $O(NM)$ time into a feasible solution. For typical network scenarios, the solution thus computed is numerically shown to be very close to the optimal solution with no restrictions.

The SC-FDMA (single-carrier frequency division multiple access) is the access scheme that has been adopted by 3GPP (3rd generation partnership project) for the LTE (long term evolution) uplink. The SC-FDMA is an attractive alternative to OFDMA (orthogonal frequency-division multiple access) especially on the uplink owing to its low peak-to-average power ratio. This fact increases the power efficiency and reduces the cost of the power amplifiers at the mobile terminals. The use of SC-FDMA on the uplink implies that for highly loaded cells the base station allocates a single subcarrier to each user. This results in the limitation of the achievable rate on the uplink. In this work, we propose a coalition game between mobile terminals that allows them to improve their performance by sharing their subcarriers without creating any interference to each other. The proposed scheme allows a fair use of the subcarriers and leads to a significant capacity gain for each user. The cooperation between the nodes is modelled using coalitional game theory. In this game, each coalition tries to maximize its utility in terms of rate. In the absence of cooperation cost, it can be shown that the grand coalition is sum-rate optimal and stable, i.e., the mobile terminals have no incentive to leave the grand coalition.

When a mobile operator migrates its network from the third generation (3G) system to Long Term Evolution (LTE), both 3G and LTE will coexist for a period of time. Since the 3G circuit-switched (CS) voice mechanism is more mature and available than that for the LTE Voice over Internet Protocol (VoIP), the operator may consider CS fallback (CSFB) as a solution for providing reliable voice calls. According to the 3G Partnership Project (3GPP) CSFB procedure, when a mobile user in the LTE network has an incoming or an outgoing call, the user equipment (UE) falls back from LTE to Universal Mobile Telecommunications System (UMTS). When the call is complete and released, the UE immediately returns to LTE. If the next activity for the UE is another voice call, immediately switching from UMTS to LTE may not be efficient. In this case, the UE has to perform another CSFB. To resolve this issue, we suggest delaying the returns to avoid unnecessary CSFBs, which is called delayed return (DR). Based on the measurements from the real UMTS and LTE networks, we develop an analytic model for investigating the performance of the CSFB with DR. This paper indicates that the DR scheme can effectively reduce the CSFB costs by up to 60%.

The UMTS Long Term Evolution (LTE) is an emerging technology in the evolution of 3G networks. LTE runs on an advancement of the obtainable UMTS infrastructure already used by over 80 percent of mobile subscribers worldwide. We have very inadequate resources in cellular technologies and it is important to utilize them with high efficiency. Single Carrier Frequency Division Multiple Access (SC-FDMA) & Orthogonal Division Multiple Access (OFDMA) are most important division of LTE. OFDMA was well utilized for achieving high spectral efficiency in communication method. SC-FDMA is introduced in recent times and it became handy candidate for uplink multiple access scheme in LTE system that is a project of Third Generation Partnership Project (3GPP). The Multiple Access Scheme in Advanced Mobile radio system has to meet the challenging requirements for example high throughput, fine robustness, capable Bit Error Rate (BER), high spectral efficiency, small delays, low computational difficulty, less Peak to Average Power Ratio (PAPR), low error probability etc. In our paper, we investigate the performance of SC-FDMA in LTE physical layer by considering different modulation schemes (QPSK, 16QAM and 64QAM) on the basis of BER vs Eb/No. Additive White Gaussian Noise (AWGN) and fading channel are used to evaluate the performance in presence of noise and fading.

Channel interpolation for LTE uplink systems with high mobility using Slepian sequences

The polar transmitter is an alternative RF transmitter architecture solution to achieve a high-efficiency power amplifier. In this paper the impact of polar transmitter imperfections on the UTRA long term evolution (LTE) link level performance is investigated. The most common imperfections in a polar transmitter are modelled, such as timing delay alignment and power amplifier non-idealities. Our approach is to analyze the relation between error vector magnitude (EVM) and link performance loss due to each imperfection. The results obtained are based on LTE uplink parameter settings and show that the most severe polar transmitter problem in LTE uplink is the timing delay alignment, especially for higher order modulation and coding scheme. Results also show that the EVM is a good direct measure to estimate the link level performance loss for various imperfections in the anticipated EVM range. For 16 QAM rate 3/4, an SNR loss of approximately 0.5 dB can be estimated by an EVM value of 8%.

Long Term Evolution (LTE) has adopted Single Carrier Frequency Division Multiple Access (SCFDMA) technique for uplink and Orthogonal Frequency Division Multiple Access (OFDMA) for downlink. SCFDMA is often called as Discrete Fourier Transform (DFT) spread OFDMA. In this paper, Wavelet based SCFDMA is proposed for analyzing Bit Error Rate (BER) performance. Analysis is carried out using different wavelets and different modulation schemes under AWGN channel. This analysis will show that the reduction in BER takes place by using wavelet transform in SCFDMA. Thus wavelet based SCFDMA provides better BER performance than that of DFT based SCFDMA.

The purpose of the paper is to examine if public long term evolution (LTE) network is suitable for smart grid (SG) automatic metering usage, in a suburban scenario, without causing significant hindrance to typical LTE traffic. In addition, the same generalized suburban scenario is evaluated with a hybrid sensor - LTE network where wireless sensor network (WSN) cluster heads are also equipped with LTE remote terminal units (RTUs). The simulation topology is formed as a suburban area that consists of single RTU per apartment/house for SG traffic and an average 3.7 people per habitat, each with their user equipment, using one of the available carriers. Normal SG traffic is generated in both directions, uplink and downlink. The worst-case usage factor is considered as a power outage, where all SG meters in the area of influence simultaneously detect and attempt to report such a failure. Thus, emergency SG traffic is generated simultaneous by all RTUs. To alleviate the problem of the high momentary SG emergency traffic load, two distinct solutions are proposed and simulated. As the first solution, an artificial, up to one-second random delay is introduced in the transmission scheduling of emergency messages. The second solution applies low-power WSNs at the cluster level and cluster heads that contain both 802.15.4 and LTE communication interfaces, i.e., a hybrid sensor-LTE network. The simulation results show that both of the solutions that try to alleviate the high instantaneous traffic loads can reach the quality of service criteria for SG traffic without compromising other public LTE traffic. The deciding factor to use either pure LTE approach or a hybrid sensor-LTE network comes from non-functional requirements of the system.