A complementary codes‐based CDMA architecture for wideband mobile internet with high spectral efficiency and exact rate matching

Future wireless communication systems ought to offer a high spectral efficiency and an inherent flexibility to carry diverse services with variable rate requirements. The rate change should be made scalable, continuous and real-time based to match exactly to the required data rate for conservation of precious bandwidth. The rate change in multiples of two, as implemented in the existing 3G W-CDMA standard, is undesirable. It is also preferred that the multiple access technique itself should support asymmetrical traffic in up- and down-links to fit connection modes of the Internet services. This paper is a review of our recent research effort to propose an innovative CDMA architecture based on complete complementary codes, which can satisfy major requirements for the future mobile Internet applications. The architecture uses a new "offset stacked" spreading technique, based on which both high spectral efficiency and scalable rate-matching are guaranteed. To measure spectral efficiency of the systems, "spreading efficiency" (SE) is defined as the information bit(s) conveyed by each chip. All traditional CDMA-based standards offer an SE of 1/N, where N is the processing gain. On the contrary, the SE of the proposed architecture can be made as high as one. As the bandwidth of a CDMA system is determined by its chip width, a high SE means a high spectral efficiency. This paper illustrates that the proposed scheme is well-performing and has a great potential for applications in future wireless communications beyond 3G.

We present a multiple-input-multiple-output (MIMO) code-division-multiple-access (CDMA) communication system based on complete complementary (CC) codes (CC-CDMA) in a time-dispersive (i.e. frequency-selective fading) channel. This system utilizes a novel combination, which consists of orthogonal CC codes for data spreading and a suitably designed multiuser-detector (MUD) algorithm, in order to enhance the current 3rd generation (3G) mobile systems. The simulation results for the CC-CDMA system, obtained in a frequency-selective fading channel, reveal significant improvement in bit-error-rate (BER) performance, and consequently the achieved high data rates (HDR) compared with a conventional Walsh codes based MIMO CDMA (Walsh-CDMA) system.

Internet based applications are mostly based on a reliable transport service. TCP (transmission control protocol) is one of the protocols responsible for applications performance. Mobile users access to Internet services through 2.5 and 3 Generation networks, which have a significant latency due to error mechanisms introduced at the link layer, as well as transmission delays in the radio access networks. High latency produces interaction with timers of upper protocols. Data rate is other limiting characteristic on these networks. Moreover, data rate changes during a TCP connection due to mobility. TCP can adapt its rate when slow data rate changes thanks to its self-clocking propriety. In case of a sudden change, TCP performance is degraded due to spurious retransmission, and the activation of its congestion control mechanisms. This paper will show the effects and optimization of some TCP parameters over GPRS (general packet radio service) and 802.11b real networks.

The present paper gives an overview of multiple access techniques proposed for the uplink in future wireless communication systems. This paper provides the comparison between Orthogonal Frequency Division Multiple Access (OFDMA) and Single-carrier frequency division multiple access (SC-FDMA) techniques. A survey of Uplink Multiple Access Techniques in LTE Mobile Communication System, their basic features and various issues related to this have been introduced in this paper.

The phase 1 upgrade of the ATLAS [1] pixel detector will be done by inserting a fourth pixel layer together with a new beampipe into the recent three layer detector. This new detector, the Insertable B-Layer (IBL) should be integrated into the recent pixel system with as few changes in services as possible, but deliver some advantages over the recent system. One of those advantages will be a new data transmission link from the detector modules to the off-detector electronics, requiring a re-design of the electro-optical converters on the off-detector side. First ideas of how to implement those, together with some ideas to reduce cost by increasing the systems throughput are discussed.

Orthogonal frequency-division multiplexing (OFDM) is a very attractive transmission technique for future high data rate wireless multimedia communication systems. OFDM has been developed for wideband wireless digital communication and is used in applications such as Digital Video and Audio Broadcasting (DVB, DAB, respectively), wireless networking and broadband Internet access [1]-[3].OFDM has advantages, such as high spectral efficiency, easy adaptation to severe channel conditions without complex equalization, and efficient implementation using fast Fourier transform (FFT). However, it also has some disadvantages, such as sensitivity to frequency offset, a high peak-to-average-power ratio (PAPR) and sensitivity to noises [1], [4], [5].As discussed in Chapter 3, OFDM is successfully used in MIMO systems. This chapter is devoted to investigate the various RF impairments, specifically noise and nonlinearity, and their mutual impacts on OFDM transceivers.KeywordsRadio FrequencyPhase NoisePower AmplifierAmplitude NoiseOFDM SystemThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this work, group‐wise successive interference cancellation (GSIC) scheme for multi‐rate CDMA systems is proposed. A multi‐rate CDMA system is a CDMA system that can support voice users together with data users which may have different data rates. In the proposed group‐wise detection, users with the same information rate are grouped and detected together. Users with the highest information rate are detected first, neglecting the presence of the other users in the system. Interference between the groups is cancelled in a successive order. The proposed scheme is based on the minimum mean square error (MMSE) criterion. We also studied the decision feedback interference cancellation for multi‐rate CDMA systems. The performance of the proposed detection scheme is compared with that of conventional detector, the decorrelating detector, and the linear MMSE detector for multi‐rate CDMA systems. The proposed scheme achieves better performance than the above‐mentioned detectors. The proposed scheme also provides significantly high spectral efficiency under certain conditions. The algorithms in the proposed scheme are suitable for both terrestrial and satellite applications of multi‐rate CDMA systems. Copyright © 2003 John Wiley & Sons, Ltd.

The complexity and variability of streaming data have brought a great challenge to the elasticity of the data processing systems. Streaming systems, such as Flink and Storm, need to adapt to the changes of workload with auto-scaling to meet the QoS requirements while saving resources. However, the accuracy of classical models (such as a queueing model) for QoS prediction decreases with the increase of the complexity and variability of streaming data and the resource interference. On the other hand, the indirect metrics used to optimize QoS may not accurately guide resource adjustment. Those problems can easily lead to waste of resources or QoS violation in practice. To solve the above problems, we propose AuTraScale, an automated and transfer learning auto-scaling solution, to determine the appropriate parallelism and resource allocation that meet the latency and throughput targets. AuTraScale uses Bayesian optimization to adapt to the complex relationship between resources and QoS, minimizing the impact of resource interference on the prediction accuracy, and a new metric that measures the performance of operators for accurate optimization. Even when the input data rate changes, it can quickly adjust the parallelism of each operator in response, with a transfer learning algorithm. We have implemented and evaluated AuTraScale on a Flink platform. The experimental results show that, compared with the state-of-the-art method like DRS and DS2, AuTraScale can reduce 66.6% and 36.7% resource consumption respectively in the scale-down and scale-up scenarios while ensuring QoS requirements, and save 13.5% resource on average when the input data rate changes.

Nowadays, vehicles are not only merely used as a transportation medium, but also as a highly mobile Internet of Things (IoT) node, collecting data from all types of sources. The delivery of aggregated vehicle sensor data into the cloud for further analysis is very fragile, as vehicles move fast in their environment and channel conditions vary heavily. Next to mastering possible packet loss, communication protocols need to quickly adapt to the frequent data rate changes. Random Linear Network Coding (RLNC) has been proven as an efficient and robust mechanism for reliable data transfer especially on lossy channels. In this paper, the authors extend the Scalable Network Coding (ScalaNC) framework with the novel congestion control Bottleneck, Bandwidth and Round-Trip Time (BBR) in order to quickly adapt to the frequent changes in data rate and allow effective transfer of high amounts of data from vehicles and into the cloud. ScalaNC is validated in a Hardware-in-the-Loop field test consisting of a Long Term Evolution (LTE) base station and channel emulator.

With the emergence of new applications (eg, extended reality [XR] and haptics), which require to be simultaneously served not just with low latency and sufficient reliability, but also with high spectral efficiency, future networks (ie, 6G and beyond) should be capable of meeting this demand by introducing new effective transmission designs. Motivated by this, a novel modulation technique termed as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM‐SPM) is proposed for providing highly spectral‐efficient data transmission with low‐latency and less‐complexity for future 6G wireless communication systems. OFDM‐SPM utilizes the power of subcarriers in OFDM blocks as a third dimension to convey extra information bits while reducing both complexity and latency compared to conventional schemes. In this article, the concept of OFDM‐SPM is introduced and its validity as a future adopted modulation technique is investigated over a wireless multipath Rayleigh fading channel. The proposed system structure is explained, an analytical expression of the bit error rate (BER) is derived, and numerical simulations of BER and throughput performances of OFDM‐SPM are carried out. OFDM‐SPM is found to greatly enhance the spectral efficiency where it is capable of doubling it. In addition, OFDM‐SPM introduces negligible complexity to the system, does not exhibit error propagation, reduces the transmission delay, and decreases the transmission power by half.

Some signal design methods for the approximately synchronized CDMA systems based on complete complementary codes have been proposed. It has been shown that estimating the multipath channels and applying the convolution of the spread-time signals can increase both the information transmission rate and the frequency usage rate. It is also pointed out that the dynamic range of the signals needs to be constrained before transmission in these methods because the convoluted information signals often have a very large value at each chip. This is a very serious problem in the actual communication systems. In this paper we consider two of those signal design methods using complete complementary codes. The efficiency of the communication systems using these two methods are analyzed and compared through some numerical simulations. The influences of the signals with constrained dynamic range are also included.

Summary form only given. Emerging demands for high data rate multimedia based services and high spectral efficiency are the key drives for the continued technology evolution in wireless communications. Recently, several advancements have been introduced for 3G wireless communication systems to further enhance the data rate and the system performance. However, due to the proliferation of wireless multimedia applications and services such as video teleconferencing, network gaming, and high-quality audio/video streaming, it is apparent that 3G wireless systems will be unable to comply with this ever increasing demand for broadband wireless services. The next generation wireless communication systems (namely, fourth generation (4G) or beyond 3G (B3G) systems) are expected to support much higher data rate services compared to evolving 3G systems (up to 100 Mbit/s in outdoor environments and up to 1 Gbit/s in indoor environments). The major technical challenges will be achieving high spectral efficiency and handling high frequency-selectivity due to the use of large bandwidth. Hence, it has become crucial to incorporate the recent technical advances in the physical layer into the future wireless systems. In this keynote speech, an overview of leading technological advances and future trends in the physical layer that enable truly ubiquitous broadband wireless capabilities will be presented. The topics include multiple-input multiple-output (MIMO) technologies, adaptive modulation, cooperative diversity, multicarrier CDMA, ultra wideband (UWB) transmission, and cognitive radio.

In order to solve the high bit error rate (BER) caused by rate oscillation in traditional Data Rate Change (DRC) algorithm, an improved DRC algorithm based on Adaptive Frame Length (AFL) was proposed. Firstly, the frame length and transmission rate of the initial transmission were determined by the parameters of the current channel and the information of previous empirical values. Then, if two frames with the same length were successively sent in the transmission process, the frame length would be accordingly increased. If the retransmission failed twice in a row, the frame length would be halved in the next transmission. Finally, the frame error rate was calculated based on the current frame length. The data rate would be updated If the value was less than the present threshold. Compared with RapidM DRC, the average bit error rate of the link decreased by 4.8 percentage points, and the link availability increased by 10 percentage points. The experimental results show that the proposed algorithm can eliminate the rate oscillation and improve the communication capability of the HF communication system.

The HF radio band is very important for military operations, enabling communications beyond line-of-sight. To deal with the variability of the Ionosphere, several technologies have emerged in the last years, like automatic Link Quality Analysis (LQA), Automatic Link Establishment (ALE) and Data Rate Change (DRC) algorithms. In this paper, two DRC algorithms are assessed — namely, Trinder and RapidM — and improved versions of these algorithms are proposed: Avoiding Cut-Off State (ACOS) and Bit Error Optimization (BEO). The first proposal reduces the occurrences of link cut-offs (corresponding to bit error rates higher than 10−3); the second proposal, besides increasing the link availability, eliminates data rate oscillations. When compared to the original versions of the algorithms, both proposals showed significant improvements in all of the considered link assessment metrics, either when evaluated in a simulation environment, or in real field propagation tests.

In this paper, we consider SC-FDE schemes (Single Carrier with Frequency-Domain Equalization) employing OQPSK (Offset Quaternary Phase Shift Keying) signals with quasi-constant envelope. To allow high spectral efficiency, different frequency channels are separated by the symbol rate, regardless of their bandwidth (which is much higher than the symbol rate for quasi-constant envelope OQPSK signals), and we consider a multi-channel frequency-domain receiver with ACI (Adjacent Channel Interference) suppression. Our performance results show that it is possible to have high spectral efficiency with quasi-constant envelope OQPSK signals. This technique is especially interesting for the uplink of future broadband wireless systems since we can employ low-cost, grossly nonlinear power amplifiers at the mobile terminals and almost all signal processing is shifted to the base station.