Long Term Evolution-Advanced Uplink Research Articles

Energy-efficient power allocation for massive M2M communication over LTE-A cellular uplink

In order to enable massive machine-to-machine (M2M) communication in Long Term Evolution-Advanced (LTE-A) cellular network, a machine-type communication gateway (MTCG) is introduced to solve the issue of control signaling overheads. In this paper, a power allocation algorithm based on the method of Lagrange multipliers is proposed for massive M2M communication over LTE-A cellular uplink. The proposed algorithm can decrease the signaling overheads by enabling the machine-type communication device (MTCD) to access the base station (BS) via a MTCG that collects the data from a group of M2M devices and forward it to the BS. The core objective of the proposed algorithm is to maximize the total energy efficiency of a group of M2M devices, while satisfying the time delay of the M2M devices, by coordinating the power transmission of the MTCDs and the MTCG. The simulation results demonstrate that the proposed algorithm outperforms the heuristic algorithm and has relatively close performance to the optimal design.

NOVEL MULTIPLE LEVEL SUBCARRIER ALLOCATION SCHEME IN SC-FDMA FOR LTE-A UPLINK

Long Term Evolution-Advanced (LTE-A) uses Single-Carrier Frequency Division Multiple Accesses (SC-FDMA) for uplink, because it has robust performance against the Peak Average Power Ratio (PAPR), compared to Orthogonal Frequency Division Multiple Access (OFDMA). SC-FDMA schemes include Interleaved FDMA (IFDMA) and Localized FDMA (LFDMA), both of which are commonly practiced in LTE-A uplink. IFDMA allocates distributed frequency carriers for users, whereas LFDMA allocates localized frequency carriers for users. The frequency allocation in an IFDMA scheme exhibits better PAPR performance, whereas the advantage of LFDMA is its lower complexity requirements. In this paper, a new scheme is introduced that integrates IFDMA and LFDMA by using a variable interleave allocation of subcarriers in the bandwidth. Here, Generalized Interleaved Frequency Division Multiple Accesses (GIFDMA), is used as a master key that controls the allocation for interleaved and localized FDMA, also known as L/I FDMA. This integration of IFDMA and LFDMA has been derived theoretically and empirically. Simulations are conducted to investigate the effect of different parameters on the GIFDMA PAPR performance, which is compared to that of conventional IFDMA and LFDMA. The simulation results revealed that the proposed GIFDMA provides PAPR performance comparable to that of both LFDMA and IFDMA.

Cooperative diversity scheme using virtual MIMO antenna array in a LTE-A uplink system

This paper proposes an effective cooperative communication scheme to obtain high reliability in a long-term evolution-advanced (LTE-A) uplink system. The proposed scheme constitutes the virtual multiple input multiple output antenna array by the cooperative communication scheme and suggests the transmission signal configuration applying spatial phase coding (SPC) with the modified hierarchical modulation. In the proposed transmission signal configuration, high diversity gain is provided by the SPC scheme and the data rate is improved by modified hierarchical modulation. The modified hierarchical modulation transforms the constellation of the conventional hierarchical-modulated signal in order to minimize the influence by noise in the proposed scheme. In the LTE-A uplink system, the proposed scheme is effective to a user equipment (UE) based on single carrier-frequency division multiple access because UE using only single antenna can obtain high reliability without additional antennas.

A resource allocation scheme for device-to-device communications using LTE-A uplink resources

Device-to-device (D2D) communications enabling devices to directly communicate with each other have been considered to overcome the shortage of available radio resource and reduce heavy traffic load on cellular base station. D2D communications operating on cellular networks can improve the efficiency of utilizing radio resource by reusing the resource of cellular networks. However, it can cause interference between cellular and D2D entities using the same resource, and the interference may degrade the performance of the entire system. D2D communications have been preferred to use uplink (UL) resources of cellular networks due to asymmetric UL and downlink (DL) service loads. In Long Term Evolution Advanced (LTE-A), single carrier frequency division multiple access (SC-FDMA) has adopted as UL transmission scheme in order to achieve low a high peak-to-average power ratio (PAPR). There are the exclusivity and the adjacency constraints in SC-FDMA. In order to enable D2D communications to efficiently reuse UL resources of the cellular networks, a radio resource allocation scheme with the constraints of SC-FDMA is proposed in this paper. The proposed scheme pairs up a cellular user equipment (CUE) and a D2D pair as a resource sharing pair (RSP) by controlling transmission power of D2D user equipments (DUEs), and allocates the contiguous subchannels to an RSP based on the well-known proportional fairness (PF) scheduling algorithm. The results of performance evaluation show that the proposed scheme can maintain throughputs of CUEs and alleviate the high PAPR problem of user equipments (UEs).

First LTE-Advanced Commercial Network Deployed [Mobile Radio

The Russian operator YOTA Networks and Huawei Technologies Company, Inc. announced the launch of what they claim is the world's first long-term-evolution-advanced (LTE-A) commercial network in Moscow. Huawei modernized its end-toend single radio-access network (RAN) LTE/Evolved Packet Core solution for LTE-A [in terms of 3rd Generation Partnership Project (3GPP) rev10]. The solution features carrier aggregation technology, which provides downlink peak rates of up to 300 Mb/s, depending on the capacity of the radio channel. Huawei also announced that it has successfully conducted what it claims is the world's first LTE-A uplink coordinated multipoint (CoMP) trial on several commercial LTE networks in Europe and Asia. The results showed that uplink CoMP can effectively double data rates at cell edges for a single user, improving network performance in terms of coverage, spectrum efficiency, and throughput.

On the Feasibility of Precoded Single User MIMO for LTE-A Uplink

The 3rd Generation Partnership Project (3GPP) is currently specifying the system requirements for Long Term Evolution - Advanced (LTE-A), having as a target peak data rates of 1 Gbit/s in local areas and 100 Mbit/s in wide areas. To meet these ambitious requirements for the uplink, multiple-input-multiple-output (MIMO) antenna techniques are expected to be deployed. In this paper, several channel-aware MIMO precoding techniques are presented. Specifically, precoded single user spatial multiplexing for both Orthogonal Frequency Division Multiplexing (OFDM) and Single Carrier Frequency Division Multiplexing (SCFDM) is studied, and its feasibility in a LTE-A uplink system is discussed. Particular emphasis is given to the limited feedback precoding, where a codebook generation method based on the Lloyd algorithm is proposed. Results show that, when full channel knowledge is available at both the transmitter and the receiver, precoding leads to a spectral efficiency gain up to 4 dB over open loop transmission; furthermore, OFDM slightly outperforms SC-FDM because of its higher robustness to the noise. Limited feedback precoding has been shown to be effective and consistently robust to the subcarrier grouping in a urban micro scenario. However, the performance is severely degraded in the blind precoding case, where transmitter and receiver compute the precoding matrix independently, due to the high sensitivity to the delay. Finally, the precoding operation over the SCFDM signal is shown to increase its Peak to Average Power Ratio (PAPR), thus reducing its advantage with respect to OFDM.