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Neural Networks and Adaptive Signal Processing
Published in Richard C. Dorf, Circuits, Signals, and Speech and Image Processing, 2018
Jose C. Principe, Mohamed Ibnkahla, Ahmad Iyanda Sulyman, Yu Cao
Classical wireless designs are based, in general, on the worst-case scenario. This leads to nonefficient use of resources. Wireless link adaptation can be defined as any alteration of the transmitter parameters based on information about the channel and network conditions. Methods of adaptation can be classified by the type of adaptation performed (e.g., power, modulation, code rate, etc.). Similar to what has been discussed in previous sections, adaptation can be exploited because of the time-varying nature of the channel, traffic changes, user needs, and QoS requirements. However, this time-varying nature makes the efficiency of the adaptation process dependent on the quality of the measurements and the delays in transmitting the necessary information to the transmitter. Figure 22.36 displays the principle of adaptive modulation and coding schemes.
Autonomic Network Management
Published in Hrishikesh Venkatarman, Ramona Trestian, 5G Radio Access Networks: Centralized RAN, Cloud-RAN, and Virtualization of Small Cells, 2017
The term link adaptation, in its broader sense, denotes the matching modulation, coding, and other signal/protocol parameters to condition the radio link. This task may be carried out by the adaptive modulation schemes, where the channel quality indicator (CQI) is derived from signal-to-interference-plus-noise ratio (SINR) measurements made by the receiver. There are various adaptation approaches such as (1) fixed link adaptation, (2) differentiated link adaptation, (3) fast link adaptation, and (4) window-based link adaptation. In this work, we consider an extended version of the link adaptation definition, that is, where the link adaptation local objective function is not confined to physical-level characteristics, instead it should encamp both the channel condition and backhaul network conditions. Furthermore, for solutions implementing simultaneous connectivity over multiple interfaces, in which case the proposed link adaptation incorporates the load balancing (over homogeneous/heterogeneous wireless access networks and in the core network) concepts at the network side and maintains the user satisfaction at the user side.
Link Adaptation Mechanisms in WirelessMAN
Published in Yan Zhang, Hsiao-Hwa Chen, Mobile Wimax, 2007
Gurkan Gür, Fatih Alagöz, Tuna Tugcu
The basic rationale behind link adaptation is to optimize throughput by selecting among the set of available rates, as given by a set of modulation and coding schemes, the one that maximizes the throughput in each “short-term” channel state [1]. In other words, the communication system utilizes higher modulation levels and higher channel coding rates when the channel condition is favorable and lower modulation levels and lower channel coding rates when the channel condition is relatively harsh [2]. Therefore this capability is crucial to cope with adverse channel conditions, especially in wireless communication systems such as wirelessMANs.
Performance analysis of 802.11n-based cognitive wireless system with joint rate and power adaptation
Published in International Journal of Electronics, 2020
Santosh Itraj, Uttam Bombale, Pravinkumar Patil, Meenakshi Patil
Orthogonal Frequency Division Multiplexing (OFDM) is a promising candidate for the CR system due to low inter-symbol interference (ISI), low inter-carrier interference (ICI) and flexibility in dynamic allocation of the resources among the channels ‘(Weiss et al., 2004)’. Many researchers have proved link adaptation as a key technique to improve the performance of the OFDM-based wireless communication systems ‘(Saoucha et al., 2016)’. However, link adaptation in the case of the OFDM-based CR network is the most challenging task due to the dynamic wireless environment. The link adaptation strategies adapt modulation, coding rate, and the transmit power to improve the throughput, BER, and the energy efficiency of the system. Power adaptation can be used either to maximise the capacity or to minimise energy consumption.
Integrated scheduling and link adaptation for heterogeneous networks: design and performance analysis
Published in International Journal of Electronics, 2020
Mehrdad Taki, Mohammad Bagher Nezafati
In recent years, heterogeneous networking has been identified as an emerging architecture for future communication networks, in which various communicating nodes require different services and can exploit diverse time-varying communication channels. Scheduling or user selection scheme is an important issue in wireless networks which assigns the time or frequency resources of wireless medium to users with taking into account the user requirements. Link adaptation is a technique for high-performance communications that adapts the transmission rate and power according to the channel state. Two approaches to link adaptation, i.e. continuous and discrete, are used. In continuous link adaptation, the transmission rate is continuously adapted based on the channel signal-to-noise ratio (SNR), and this approach, though insightful for system performance analysis, is not implementable in practical systems. In discrete link adaptation, a small bit error rate (BER) is accepted, and the transmission rate is chosen from a limited set of discrete rates (Chung & Goldsmith, 2001). Discrete rate adaptation is utilised in third-generation partnership project (3GPP) long-term evaluation (LTE) with quadrature phase-shift keying/quadrature amplitude modulation (QPSK/QAM) and Turbo coding (3GPPTS36.212, 2016).
Delay constrained throughput optimisation with imperfect CSI using discrete adaptive power
Published in International Journal of Electronics, 2018
Mehrdad Taki, Mohammad B. Nezafati
Efficient utilisation of limited and shared wireless resources becomes an inevitable necessity due to increasing demands for wireless, especially mobile applications. In link level transmission performance analysis (L. Chen, 2011), link adaptation is an enabling method to improve the throughput of a wireless link by adjustment of the transmission rate and/or power at the transmitter based on the estimated channel state fed back from the receiver (Chung & Goldsmith, 2001). The current article presents novel and efficient schemes for link adaptation in a wireless link considering practical constraints and imperfections.