Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years

Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions

OFDMA/SC-FDMA aided space-time shift keying for dispersive multi-user scenarios

Motivated by the recent concept of Space-Time Shift Keying (STSK) developed for achieving a flexible diversity versus multiplexing gain trade-off, we propose a novel Orthogonal Frequency Division Multiple Access (OFDMA)/Single Carrier Frequency Division Multiple Access (SC-FDMA) aided multi-user STSK scheme for frequency-selective channels. The proposed OFDMA/SC-FDMA STSK scheme is capable of providing an improved performance in dispersive channels, while supporting multiple users in a multiple antenna aided wireless system. Furthermore, the scheme has the inherent potential of benefitting from the low-complexity single-stream Maximum-likelihood (ML) detector. Both an uncoded and a sophisticated near-capacity coded OFDMA/SC-FDMA STSK scheme were studied and their performances were compared in multiuser wideband Multiple-Input Multiple-Output (MIMO) scenarios. Explicitly, OFDMA/SC-FDMA aided STSK exhibits an excellent performance even in the presence of channel impairments due to the frequency-selectivity of wideband channels and proves to be a beneficial choice for high capacity multi-user MIMO systems

A Review on OFDMA and MU-MIMO MAC Protocols for upcoming IEEE Standard 802.11ax

IEEE introduced a new standard IEEE 802.11ax for the next generation WLANs.As we know,the current throughput is very low because of the current Media Access Control(MAC) in present wireless area networks.So,the concept of Orthogonal Frequency Multiple Access(OFDMA) to facilitate multi user access is introduced.The main challenges of adopting OFDMA areoverhead reduction and synchronization.To meet these challenges this paper revised an OFDMA based OMAX protocol.And due to various various bandwidth consuming applications and devices today’s WLANs have become stressed and low at throughput.To handle this problem MU MIMO is used to improve the performance of WLANs.This paper surveys uplink/downlink mutli user MAC protocols for MIMO enabled devices.It also identifies the key requirements of MAC protocol design

JOINT TIMING SYNCHRONIZATION AND CHANNEL ESTIMATION USING PERFECT SEQUENCE IN UPLINK TIME DOMAIN SYNCHRONOUS OFDMA

Time Domain Synchronous Orthogonal Frequency Division Multiple Access (TDS-OFDMA) is used in mobile broadband wireless access scheme in uplink transmission. This leads to multiple user interference due to timing offset and frequency offset. In this paper, the effect of timing offset and channel estimation in mobile broadband system is analysed. Time-space two dimensional structure is used in TDS-OFDMA and perfect sequence is used for guard interval to achieve perfect timing synchronization and channel estimation for each user. Simulations are performed for timing synchronization and channel estimation using perfect sequence under Urban channel, Indoor Office B channel and HIPER LAN-A channel. Simulation results show that the timing synchronization is achieved and channel estimation performance using perfect sequence is better than CAZAC and PN Sequences