6 research outputs found
Trellis-based iterative decoding of block codes for satellite ATM
In power-limited channels such as satellite links, error control codes are needed to provide high performance at very low Signal-to-Noise Ratios (SNRs). Turbo Codes or concatenated codes with iterative decoding, can achieve a performance very close to the Shannon limit. They are the most powerful codes known so far and are considered for use in various applications. In this thesis, we present the turbo codes using Reed-Muller (RM) codes as their component codes, and where the decoding method used is the trellis-based iterative Maximum A posteriori Probability (MAP) algorithm which provides an optimal performance. We aim to apply our turbo coding scheme to Asynchronous Transfer Mode (ATM) applications in Digital Video Broadcast - Return Channel via Satellite (DVB-RCS). Therefore, the shortened versions of ordinary RM-turbo codes are proposed. As well, we investigate the effect of phase offset on the shortened RM-turbo code performance with Quadrature Phase Shift Keying (QPSK) modulation scheme and the effect of preamble size used to recover carrier phase due to the problem of synchronization which is usually raised in practical system
SCMA for Open-Loop Joint Transmission CoMP
Sparse Code Multiple Access (SCMA), a non-orthogonal multiple access scheme,
has been introduced as a key 5G technology to improve spectral efficiency. In
this work, we propose SCMA to enable open-loop coordinated multipoint (CoMP)
joint transmission (JT). The scheme combines CoMP techniques with multi-user
SCMA (MU-SCMA) in downlink. This scheme provides open-loop user multiplexing
and JT in power and code domains, with robustness to mobility and low overhead
of channel state information (CSI) acquisition. The combined scheme is called
MU-SCMA-CoMP, in which SCMA layers and transmit power of multiple transmit
points (TPs) are shared among multiple users while a user may receive multiple
SCMA layers from multiple TPs within a CoMP cluster. The benefits of the
proposed scheme includes: i) drastic overhead reduction of CSI acquisition, ii)
significant increase in throughput and coverage, and iii) robustness to channel
aging. Various algorithms of MU-SCMA-CoMP are presented, including the
detection strategy, power sharing optimization, and scheduling. System level
evaluation shows that the proposed schemes provide significant throughput and
coverage gains over OFDMA for both pedestrian and vehicular users
Uplink Contention Based SCMA for 5G Radio Access
Fifth generation (5G) wireless networks are expected to support very diverse
applications and terminals. Massive connectivity with a large number of devices
is an important requirement for 5G networks. Current LTE system is not able to
efficiently support massive connectivity, especially on the uplink (UL). Among
the issues arise due to massive connectivity is the cost of signaling overhead
and latency. In this paper, an uplink contention-based sparse code multiple
access (SCMA) design is proposed as a solution. First, the system design
aspects of the proposed multiple-access scheme are described. The SCMA
parameters can be adjusted to provide different levels of overloading, thus
suitable to meet the diverse traffic connectivity requirements. In addition,
the system-level evaluations of a small packet application scenario are
provided for contention-based UL SCMA. SCMA is compared to OFDMA in terms of
connectivity and drop rate under a tight latency requirement. The simulation
results demonstrate that contention-based SCMA can provide around 2.8 times
gain over contention-based OFDMA in terms of supported active users. The uplink
contention-based SCMA scheme can be a promising technology for 5G wireless
networks for data transmission with low signaling overhead, low delay, and
support of massive connectivity.Comment: Submitted to Golobecom 5G workshop 201
Uplink Contention Based SCMA for 5G Radio Access
Abstract Fifth generation (5G) wireless networks are expected to support very diverse applications and terminals. Massive connectivity with a large number of devices is an important requirement for 5G networks. Current LTE system is not able to efficiently support massive connectivity, especially on the uplink (UL). Among the issues that arise due to massive connectivity is the cost of signaling overhead and latency. In this paper, an uplink contention-based sparse code multiple access (SCMA) design is proposed as a solution. First, the system design aspects of the proposed multiple-access scheme are described. The SCMA parameters can be adjusted to provide different levels of overloading, thus suitable to meet the diverse traffic connectivity requirements. In addition, the system-level evaluations of a small packet application scenario are provided for contention-based UL SCMA. SCMA is compared to OFDMA in terms of connectivity and drop rate under a tight latency requirement. The simulation results demonstrate that contention-based SCMA can provide around 2.8 times gain over contention-based OFDMA in terms of supported active users. The uplink contention-based SCMA scheme can be a promising technology for 5G wireless networks for data transmission with low signaling overhead, low delay, and support of massive connectivity