A Handover Prediction Model and its Application to Link Layer Triggers for Fast Handover

Cross layer handover schemes are expected to provide seamless services to users on the move. To achieve this goal, a link layer must timely trigger handover protocols of upper layers so that they can finish necessary handover procedures before current wireless link terminates. Therefore, a mobile node needs an appropriate model to predict impending handover to generate link layer triggers in time. In this paper, we propose a mobility model that does not assume any radio propagation environments and movement patterns of a mobile node. Through statistical analysis of the received signal strength index (RSSI) datasets measured in various radio propagation environments, we validate that an adaptive autoregressive process can be used as a handover prediction model. With the proposed model, we also propose a link layer triggering scheme. Since the prediction process inevitably introduces errors, we devise a statistical compensation method to initiate link layer triggers in a timely manner considering the given handover signaling delay bound. Simulation results show that the error compensation method can significantly decrease the rate of late link layer triggers with the reasonable increase in the false alarm rate.     

Space-time frequency-shift keying

Frequency-shift keying (FSK) is a popular modulation scheme in power-limited communication links. This paper introduces space-time FSK (ST-FSK), which does not require any channel state information at the transmitter and the receiver, as in conventional noncoherent FSK. ST-FSK can be viewed as a special unitary ST modulation design. However, ST-FSK has a number of advantages over existing unitary ST modulation designs. ST-FSK is easier to design, and enjoys lower decoding complexity. Furthermore, ST-FSK guarantees full diversity. Finally, ST-FSK can be adopted in the digital as well as in the analog domain, and merges very naturally with frequency-hopping multiple access. As expected, all these advantages come at the cost of a decrease in spectral efficiency.     

Combined frequency and phase-shift keying

In previous letters, the constraints necessary for the elimination of i.s.i. in both binary and multilevel f.s.k. were discussed. It is now shown that a system with simultaneous phase and frequency modulation is possible, both modulations being detected with zero i.s.i. In terms of energy per bit required at the receiver input for a given error rate, a 4-phase 2-frequency system is shown to be superior to an equivalent 8-state multiphase or combined phase/amplitude system.     

光8DPSK调制原理及仿真

光8DPSK(optical Differential 8-Phase Shift Keying)是一种多级相位调制新码型,是光通信领域研究的前沿,文章介绍了光8DPSK调制格式原理和调制解调方式,用Matlab做了仿真,绘制出了频谱图、眼图,并对占空比为0.5的RZ-8DPSK信号做了详细分析,调制和解调了64个伪随机码序列,仿真绘制了光脉冲时序图、相位差图和平衡接收后的电信号时序图.     

Rotative quadrature phase-shift keying

A rotative quadrature phase-shift keying (RQPSK) modulation scheme is proposed. By rotating the QPSK signal constellation by pi /2 either clockwise or anticlockwise during a symbol duration, the conventional QPSK scheme can be modified to transmit 3 bits per symbol to achieve both power and bandwidth efficiency.<>     

WCDMA的软切换和TD-SCDMA的接力切换算法的分析与比较

本文首先介绍了第三代移动通信中的WCDMA、TD-SCDMA和CDMA2000,接着分别概述了WCDMA和TD-SCDMA切换的概念、过程和算法分析,最后比较了WCDMA软切换算法与TD-SCDMA接力切换算法各自的特点。     

Multifrequency minimum shift keying

A new modulation scheme that produces a constant envelope continuous phase signal set with a compact power spectrum and power efficiency better than that of MSK is proposed. The scheme can be implemented by quadrature-carrier multiplexing of two frequency/phase modulated signals of the type NFSK/2PSK, both with the same frequency in each transmission interval, and with sinusoidal symbol shapes. The generated signal can be viewed in each transmission interval as an MSK signal at one of the N frequencies and is referred to as multifrequency minimum shift keying (MF MSK). Modulation, demodulation, and synchronization circuits are described, and the spectral properties and power efficiency on the AWGN channel are analyzed. Combining a number of attractive attributes such as constant envelope, excellent spectral properties, high power efficiency, and self-synchronization capability, the proposed modulation format lends itself to a variety of applications, one of them being the digital satellite link     

Multilevel differential polarization shift keying

We analyze the performance of coherent optical communication systems which employ polarization shift keying (PolSK) modulation, introducing for the first time the requirements for multilevel, differential PolSK. For M-ary signal constellations with M>2, the three-dimensional (3-D) nature of the signal constellations within Stokes space requires the use of double-differential modulation and detection (M-DDPolSK). Coding constraints on the signals place an additional restriction on such systems. We present detailed analysis and simulations for a 6-DDPolSK modulation scheme in which the signal points are located at the vertices of an octahedron in Stokes space     

Unconventional cryptographic keying variable management

We present three unconventional approaches to keying variable management. The first approach is based on using a public key cryptosystem (PKC) that is breakable in short, but on average less, time than it takes to set up an ultrawide bandwidth modem that is then used to transport a keying variable for a classical cryptosystem. The second concept proposes using the characteristics of an urban UHF radio channel, determined by mutual sounding, as the cryptovariable. The third concept encourages research into ill-conditioned problems as potentially fruitful ground for PKCs not based on finite field arithmetic     

GSM 系统切换分析

切换是指移动用户在通话过程中变换服务信道的过程。本文介绍了切换的种类及影响切换的原因,给出了解决切换失败的方法。     

New Developments in Vertical Handover Based on Media Independent Handover Standard

This paper proposes an enhanced approach for implementation of Media Independent Handover (MIH) information services (MIIS) based of the combination of a hierarchy of information servers and prediction of next point of attachment (PoA). While other recent proposals were validated only by simulations, we evaluated the implemented system with a real video streaming application. The preliminary results show performance improvements in streaming continuity when compared with our former proposal, the prediction of PoA based on unique MIIS server. We conclude that in a more complex situations the performances could increase even more, and we draw some new development directions we want to explore in our future work.     

WCDMA与GSM系统间切换分析

WCDMA与GSM系统之问的互操作为双网合一网络运营提供了便利.本文介绍了WCDMA与GSM互操作中的切换过程,对其中几项关键技术进行了详细分析,并对切换中的性能和要点进行了探讨,为3G网络的建设发展提出了具体建议.     

基于认知的频谱切换技术

文章利用认知频谱检测、动态频谱分配、重配置等技术,考虑短时频谱特征与业务特征的匹配程度,在通信过程中网络侧选择待切换终端发起切换命令,解决由于容量受限而导致的系统过载、无法接纳新会话等问题,并在保证用户服务质量(QoS)的前提下提高切换成功率,有效消除过载现象,从而增大系统吞吐量,允许更多的会话接入,降低阻塞率,提升通信系统性能.     

IMS域的切换研究

基于IMS(IP Multimedia Subsystem)域的通信中由于切换层次的增多导致切换时间的增加,从而使得服务的中断时间加长,这影响了移动中应用的服务质量。在UMTS(Universal Mobile Telecommunication System)R6规范中的切换流程中,跨网络切换采用SGSN(Serving GPRS Support Node)之间的切换而GGSN(Gateway GPRS Support Node)不变,这会导致数据流在IP(Internet Protocol)网络中的迂回,并且多条信令跨网络传输影响了切换的速度,增加了网络流量和端到端延时。该文在现有切换流程上提出了跨GGSN的切换流程,缩短了媒体流在切换过程中的中断时间,并减少了漫游状态下的端到端媒体流引起的网络流量和端到端的数据延迟。     

Synchronization of quadrature-quadrature phase-shift keying signals

The key synchronization aspects in the system design of a QQPSK (quadrature-quadrature phase-shift-keying) modem are addressed. The sensitivity of the data demodulator to synchronization errors is discussed, and contextually the performances of some IF and baseband carrier phase and symbol timing recovery schemes are evaluated both theoretically and by computer simulations. In particular, a fourth-power IF carrier/clock regenerator and two baseband clock recovery schemes, with and without the aid of data decisions, respectively, are taken into account. The analysis shows on the one hand the substantial robustness of QQPSK to carrier phase errors and the adequacy of the examined carrier extraction scheme. On the other hand, the remarkable sensitivity of QQPSK to symbol timing inaccuracy is stressed and the need to resort to the newly proposed decision-aided baseband clock recovery scheme is pointed out     

Cognitive Spectrum Handover Technology

Based on spectrum sensing, dynamic spectrum allocation and reconfiguration technologies in Cognitive Radio (CR), this paper fully considers the matching issues between short-term spectrum characteristic and service characteristic. In the communication process, the network-side selects switch terminals to initiate handover command to solve problems due to limited capacity of the system, such as overload and new session decline, improving the success rate of switching on the premise of ensuring user’s QoS, reducing blocking probability with more session admission, eliminating overload, increasing system throughput, and improving the whole system performance.     

The cutoff rate for on-off keying

It is well known that on-off keying (OOK), i.e. the transmission of a pulse for a data one (mark) and transmission of no signal for a data zero (space), exhibits a 3 dB inferiority to antipodal signalling, in terms of the signal-to-noise ratio required to achieve a specified bit error probability. When the channel is characterized by the cutoff rate R₀, this 3 dB inferiority persists, in the sense that the required E_b/N₀ to operate at a given value of R₀ is 3 dB greater for the OOK channel than for the antipodal channel. However, it is shown that, if the definition of cutoff rate is generalized in an appropriate way to reflect the fact that signal energy is expended only in the transmission of marks, part of this penalty is recovered. In fact, it is shown that, in the limit of low R₀, there is no penalty in signal-to-noise ratio. Even at rates of realistic interest, the penalty is significantly less than the expected 3 dB     

Nonlinear continuous phase frequency shift keying

A novel signal-space coded CPM (continuous phase modulated) signaling technique, called nonlinear CPFSK (continuous phase frequency shift keying) signaling, which guarantees the maximum constraint length allowed by the number of states is introduced. Nonlinear CPFSK signals use a suitably selected state transition matrix during all signaling intervals. The selected state transition matrix is realized by changing the modulation index of the signals, hence the modulation index used during any interval depends on the transmitted symbol as well as on the state of the system. Binary nonlinear CPFSK signaling schemes are constructed and analyzed. Numerical results indicate that nonlinear CPFSK signals can achieve attractive minimum distances compared with other existing CPM signaling formats