Hyung G. Myung

Single carrier FDMA for uplink wireless transmission

Single carrier frequency division multiple access (SC FDMA), a modified form of orthogonal FDMA (OFDMA), is a promising technique for high data rate uplink communications in future cellular systems. SC-FDMA has similar throughput performance and essentially the same overall complexity as OFDMA. A principal advantage of SC-FDMA is the peak-to-average power ratio (PARR), which is lower than that of OFDMA. SC FDMA is currently a strong candidate for the uplink multiple access scheme in the long term evolution of cellular systems under consideration by the third generation partnership project (3GPP). In this paper, we give an overview of SC-FDMA. We also analyze the effects of subcarrier mapping on throughput and PARR. Among the possible subcarrier mapping approaches, we find that localized FDMA (LFDMA) with channel-dependent scheduling (CDS) results in higher throughput than interleaved FDMA (JFDMA). However, the PARR performance of IFDMA is better than that of LFDMA. As in other communications systems there are complex tradeoffs between design parameters and performance in an SC-FDMA system

Single Carrier FDMA: A New Air Interface for Long Term Evolution

Single Carrier Frequency Division Multiple Access (SC-FDMA) is a novel method of radio transmission under consideration for deployment in future cellular systems; specifically, in 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) systems. SC-FDMA has drawn great attention from the communications industry as an attractive alternative to Orthogonal Frequency Division Multiple Access (OFDMA). Introduction to Single Carrier FDMA places SC-FDMA in the wider context of wireless communications, providing the reader with an in-depth tutorial on SC-FDMA technology. The book introduces the reader to this new multiple access technique that utilizes single carrier modulation along with orthogonal frequency multiplexing and frequency domain equalization, plus its applications in communications settings. It considers the similarities with and differences from orthogonal frequency division modulation, multiplexing, and multiple access used extensively in cellular, broadcasting, and digital subscriber loop applications. Particular reference is made to the peak power characteristics of an SC-FDMA signal as an added advantage over OFDMA. Provides an extensive overview of the principles of SC-FDMA and its relation to other transmission techniques. Explains how the details of a specific implementation influence the tradeoffs among various figures of merit. Describes in detail the configuration of the SC-FDMA uplink transmission scheme published by 3GPP. Features link level simulation of an uplink SC-FDMA system using MATLAB. This is an essential text for industry engineers who are researching and developing 3GPP LTE systems. It is suitable for engineers designing wireless network equipment, handsets, data cards, modules, chipsets, and test equipment as well as those involved in designing LTE infrastructure. It would also be of interest to academics, graduate students, and industry researchers involved in advanced wireless communications, as well as business analysts who follow the cellular market.

Peak-To-Average Power Ratio of Single Carrier FDMA Signals with Pulse Shaping

Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique that has similar performance and essentially the same overall complexity as those of OFDM, in which high peak-to-average power ratio (PAPR) is a major drawback. An outstanding advantage of SC-FDMA is its lower PAPR due to its single carrier structure. In this paper, we analyze the PAPR of SC-FDMA signals with pulse shaping. We analytically derive the time domain SC-FDMA signals and numerically compare PAPR characteristics using the complementary cumulative distribution function (CCDF) of PAPR. The results show that SC-FDMA signals indeed have lower PAPR compared to those of OFDMA. Comparing the two forms of SC-FDMA, we find that localized FDMA (LFDMA) has higher PAPR than interleaved FDMA (IFDMA) but somewhat lower PAPR than OFDMA. Also noticeable is the fact that pulse shaping increases PAPR

Channel-Dependent Scheduling of Uplink Single Carrier FDMA Systems

We examine single carrier frequency division multiple access (SC-FDMA) with frequency domain equalization for uplink data transmission. We investigate channel-dependent scheduling schemes to achieve multi-user diversity and frequency selective diversity. There are two subcarrier mapping schemes in SC-FDMA: Localized FDMA (L-FDMA) and Interleaved FDMA (I- FDMA). L-FDMA benefits from frequency selective scheduling, but it incurs higher peak-to-average power ratio than I-FDMA. Throughout our work, we provide low complexity channel- dependent scheduling (CDS) methods for L-FDMA and I-FDMA. The results show that rate-sum capacity can increase up to 130% for L-FDMA and 40% for I-FDMA relative to static round robin scheduling.

PRoportional Fair Scheduling of Uplink Single-Carrier FDMA Systems

We apply novel utility-based scheduling schemes to uplink single carrier frequency division multiple access (SC-FDMA) systems. Two utility functions are used for managing two dimensional resources (time and frequency): user data rate for maximizing system capacity and logarithmic user data rate for proportional fairness. To develop utility-based scheduling algorithms, we revise channel-dependent scheduling (CDS) schemes derived in our previous work (J. Lim et al.). The results show that proportional fair scheduling with logarithmic user data rate can improve the rate-sum capacity up to 100% for localized FDMA and 30% for interleaved FDMA, with the capacity gains equally shared among all users

Peak Power Characteristics of Single Carrier FDMA MIMO Precoding System

A salient advantage of single carrier frequency division multiple access (SC-FDMA) is low peak-to-average power ratio (PAPR) which is lower than that of OFDMA. Precoding using transmit beamforming (TxBF) is a MIMO spatial multiplexing method that increases the data throughput significantly. However, when applied to SC-FDMA, it increases the PAPR. In this paper, we describe how we can apply TxBF to an SC-FDMA system and show its effect on PAPR We then consider the effects of precoder averaging across subcarriers and quantization, typically used to reduce feedback overhead, on the PAPR Comparisons are made with single antenna, non-precoded spatial multiplexing (SM) and space-frequency block coding (SFBC) systems. Lastly, we show that a modest amount of amplitude clipping can reduce PAPR to an acceptable level with virtually no harmful effects on performance or spectral growth.

Channel-Dependent Scheduling of an Uplink SC-FDMA System with Imperfect Channel Information

Channel-dependent scheduling (CDS) can increase the data throughput of a cellular system by exploiting multi-user diversity and frequency selectivity in the channel. In this paper, we investigate the impact of imperfect channel state information (CSI) on CDS. Specifically, we analyze the data throughput of an uplink single carrier FDMA (SC-FDMA) system with uncoded adaptive modulation and CDS when there is a CSI feedback delay. We consider distributed and localized subcarrier mapping schemes for resource allocation. We show that localized subcarrier mapping yields highest aggregate data throughput when we use CDS. However, we also show that localized mapping is very sensitive to the quality of CSI and the capacity gain quickly decreases when the channel changes rapidly. For high mobility users, distributed mapping with static round-robin scheduling is more suitable.

Distributed Load-Balancing in a Multi-Carrier Wireless System

We consider a cellular network or a wireless local area network (WLAN), deployed with attachment points (APs) capable of transmission and reception in multiple radio-frequency (RF) carriers. A major factor contributing to the efficiency and stability of the network is the mechanism determining the connection of terminals to the appropriate AP and the RF carrier. This paper describes a practical, distributed, network-assisted and terminal-driven mechanism to determine the connections for load-balancing among the available RF carriers. The mechanism is based on a metric that we term as the service level indicating metric (SLIM). We extend the notion of SLIM to cases where Quality-of-Service (QoS) parameters are specified and propose a load-balancing mechanism for such cases. We demonstrate the near-optimality of the proposed mechanisms through 3GPP based simulations.