Abstract—A programmable pipelined digital differentialmatchedfilter (PDMF) implemented for a direct sequence spreadspectrum receiver is proposed in this paper. To reduce the power consumption, the architecture PDMF is based on the synchro- nization combined PN code phase acquisition algorithm (Huang et al., 1999). Compared with the conventional PN code phase acquisition algorithm, the theoretical analysis result indicates that the PDMF acquires both power efficient and preferable detection. Depending on different applications, programmability allows the PDMF to implement 3-tap, 5-tap, or 11-tap Barker codes with the same hardware but different precisions for each tap coefficient. For short tap Baker codes, the architecture could adopt more precision on each tap coefficient to resist the channel noise. Simulation results also show that there are fewer errors of high sample precision with the same tape.
Low-Power Adaptive Pseudo Noise Code Acquisition forSpread-SpectrumSystems
Mau-Lin Wu and Kuei-Ann Wen
Abstract—A novel pseudo noise code acquisition combined with the newly proposed adaptive sampling rate and threshold control (ASTC) algorithm is derived for low-power spread-spectrumsystems with complementary metal–oxide–semiconductor imple- mentations. Low-power performance can be achieved by reducing the sampling rate of the proposed system while maintaining the system performance. The sampling rate is dynamically updated due to the change of the channel noise level. Under the assump- tions that the channel is additive white Gaussian noise slow-fading channel, up to 74.3% reduction in power consumption compared to the conventional fixed-sampling rate and fixed-threshold architecture is demonstrated with insignificant increase of system complexity. The proposed architecture can be applied to the design of low-power and controllable-performance spread-spectrumcommunicationsystems.
The main drawback of this SAW filter approach comes from the fact that a SAW device cannot be easily integrated with a baseband digital transversal filter in an integrated circuit (IC).
Therefore, the digital spreading code matchedfilter approach is a preferable choice when the RAKE receiver is to be im- plemented in an IC. Although current IC technology provides a large computation capability, it is still hard to implement a digital matchedfilter-based RAKE receiver on a single chip, especially when a long spreading code is used. An alternative method is to implement a RAKE receiver using a bank of cor- relators. Each correlator is used to detect a received signal path separately. The number of the correlators in the correlator bank is typically three or four. Although the correlator bank approach has low implementation complexity, it needs extra searchers to search for different multipath signals and a tracking loop for each correlator.
In Section IV, some numerical results are given and discussed.
Finally, conclusions are given in Section V.
II. N ONCOHERENT DLL
A typical digital code tracking system for DS spread spec- trum signals is shown in Fig. 1. After frequency translation, chip matched filtering, and down sampling, the code phase of the received signal is tracked by a noncoherent digital DLL. In Fig. 1, is the estimated carrier shift obtained in the code ac- quisition stage. The sampling could also be done in front of chip matchedfilter. In any case, at least two times of over-sampling is needed for proper operation of DLL. In this study, the two-times over-sampling is employed. After down-sampling, as shown in Fig. 1, the sampled signal is directed to two different routes. The integer–chip samples are directed to a despreading unit for the subsequent carrier recovery, data detection and other signal pro- cessing, and the half-chip samples (early and late samples) are directed to a digital DLL for fine code tracking.
B ANDWIDTH C OMPARISON R ESULTS B ETWEEN PSPN C ODES AND PN C ODES
Fig. 4. Plot of bandwidth versus toggle rate of the spreading codes.
The block of “frequency divider” generates the clock with data rate. PN code generator generates the PN code. Despreader is used for despreading procedure and the decision circuit detects the signal. The transistor netlist of the blocks in Fig. 6 is implemented. The circuit level simulator Hspice simulates the power consumption of the transistor netlist. All the blocks shown in Fig. 6 are included in this power consumption simulation. The circuit schematics described in Fig. 6 could be operated by different spreading codes with different code lengths. That is to say, this is a soft-coded spreadspectrum system. The simulation results of the power consumption are listed in Table IV. From Table IV, we find the percentages of reduction for power consumption range from 8% to 14% with PSPN codes compared to PN codes. The concept of low toggle rate means low-power consumption has been verified by the simulation results.
For the transmission of images over SS-CDMA AWGN channels, a subband coding scheme that divides the image information into a number of independent data streams using an analysis filter bank, each of which is multiplied by its unique signature PN code, enables the transmission of these data streams via multiple parallel virtual channels created by their correspond- ing PN codes. With a sufficiently large number of streams, the total signal is able to fit within the narrow radio channel bandwidth even though the total bandwidth of all the signals may exceed the channel bandwidth. At receiver, each received signal is separately recovered at the decoder by multiplying its PN code and integrating over the code length in order to obtain the desired subband. All the recovered subbands are then reassembled by a synthesis filter bank into a close reproduction to the original image. Additionally, for color subband image transmission, color images are first transferred to luminance (Y) and two chrominance components (I, Q). Each component is then decomposed independently into several subbands for SS-CDMA transmission. Therefore, a number of additional PN codes are required to support the transmission of the chrominance signals over the CDMA channels whereas the luminance signal was treated in the same manner as monochrome pictures. Moreover, SS-CDMA allows more than one image to be transmitted and be accessed simultaneously at the same limited channel bandwidth.
Publisher Item Identifier S 0733-8716(00)00191-8.
cars, remote hospitals, military services, homes, and office automation systems is an attractive proposition. It would free the users from cords or optical fibers tying them to particular locations within the building, thus offering true mobility which convenient and sometimes even necessary. The development of multimedia terminals will support the ever-growing demand for mixed data, audio, and video applications and will connect the portable pen pad and lap-top devices to backbone information resources and computational facilities. The possibility of multimedia services will allow services such as dial-up video conference, video-on-demand (VOD) services, and portable PC-based applications incorporating video/audio/data transfer to any location. Moreover, a number of different mobile users can simultaneously request multimedia data from one or more multimedia servers on the network. Each multimedia server is capable of catering to multiple data requests from multiple users, simultaneously. Presentation of preorchestrated multimedia information requires synchronous playback of time-dependent multimedia data according to some prespeci- fied temporal relations. At the time of creation of multimedia information, a user needs a model to specify temporal con- straints among various data objects which must be observed at the time of playback. Usually, the temporal relationships of multimedia information may be characterized by a timeline diagram which is the commonly used tool in commercial multimedia authoring products. Fig. 1 depicts an example of a timeline diagram and its associated multimedia title generated by the most commonly used product called MacroMind Di- rector. Although the timeline diagram is a useful description tool, it has a lot of redundancies in characterizing the temporal relationships and is not suitable for further analysis and system evaluation, however. To tackle this difficulty and to obtain a more compact multimedia representation, a well-known model called object-composition Petri-net (OCPN) ,  is able to describe the temporal relationships of the various components of a multimedia document and represents them in the form of a graph. Since preorchestrated multimedia information has highly time-varying bandwidth, the fixed bandlimited constant bit rate (CBR) wireless channel may not be appropriate for the variable bit rate (VBR) multimedia services. Therefore, it is desirable to design a dynamic mechanism to manage and allocate bandwidth according to the changing levels of concurrencies of multimedia data streams. Woo et al. have introduced a dynamic RF channel capacity allocation to deal with the OCPN-based multimedia data stream. In this paper, an alternative method has been proposed to provide a cost-effective resource allocation scheme for the OCPN-based multimedia services by employing the well-known antimultipath spread
Channel modeling simulation tools that enable researchers and designers to accurately predict the performance of wire- less systems become increasingly important as personal com- munications and wireless data services evolve. A basic under- standing of the channel is important not only for designing modulation and coding schemes for robust communication over such channel, but also for investigating the channel fad- ing impact on existing networking algorithms, such as rout- ing and power adjustment which critically depend on channel attenuation. At present, most network protocol simulations and even power control algorithms are using the free space (distance) channel propagation model which is basically only function of transmitter-receiver distance. Typically, for the indoor environment, the channel characteristics are much too complex to be modeled by simple distance functions. Yet, a realistic channel model is essential for network protocol eval- uation, especially in the presence of mobility. Therefore, a more realistic channel fading model which accounts for chan- nel quality variations with movement is needed for network protocol simulation.
Channel Error Analysis
Fig. 2. Digital signal flow of the proposed system.
A pair of SRRC filters with roll-off factor equal to 0.25 is used before AWG and after real-time oscilloscope, as shown in Fig 2. These two SRRC filters are capable of shrinking the signal spectrum while maintaining very low inter- symbol-interference (ISI), so it is suitable to be applied in this band-limited communication system. The pseudo random binary sequence (PRBS) was mapped to the 4-level ASK symbols. We proposed to use a symbol rate of 10M symbol/s, and by using the matchedfilter, the signal spectrum was band-limited in 10MHz. Instead of using multiple-resonant equalization circuits, the channel capacity is enhanced by using digital filters on a single LED without using optical blue filter.
VI. C ONCLUSIONS
This paper has discussed the network architecture of imple- menting networked agents as well as other networked agents for achieving the overall system performance of control and com- munication systems. Those networked agents are operating at the so-called sensor bus or field bus to execute time-critical tasks with real-time continuous system variables. The key compo- nents needed in a networked agent and the performance anal- ysis of a network-type system are then addressed. Based on the standard control design framework, this paper also presented the standard and networked MIMO system models for adap- tive communication module design. The two key features of the communication design are the integrated network and con- trol design chart, and the utilization of deadband control and state estimation. By visualizing the operating range of a net- work and control design chart, deadband controller and state es- timator can be used to decouple the sampling rate and transmis- sion rate and to dynamically adjust the communication mech- anism based on the required control and communication per- formance. Stability and performance analysis of the integrated control and communication system are also provided. Finally, this paper presented a network and control simulator developed on the Matlab/Simulink platform with commutation modules as well as control dynamics modules. The simulation tool was de- veloped to help analyze and visualize the performance of pro- posed design schemes. Both the analysis and simulation results showed the tradeoff of designing the adjusting mechanism be- tween control and communication performance.
The state of receiver channel of a wireless communication system estimated by the method of Differential Kalman filter is
investigated in this paper. The purpose of this study is expected that the system performance of wireless communication system can be improved. On the other hand, the system bit error rate (BER) can be reduced by using the proposed algorithm. Both of the application in the traditional Kalman filter scheme and the Differential Kalman filter are proposed and applied in estimation the state of communication channel in this paper, and the Rayleigh fading channel is assumed in the approach. There are about one to 3 dB gain is obtained forDifferential Kalman filter after our numerical analytic. Beside that, the later has own much simply algorithm than the former.
SUMMARY In deep-submicron technology, several state-of-the-art ar- chitectural synthesis flows have already adopted the distributed register ar- chitecture to cope with the increasing wire delay by allowing multicycle communication. In this article, we regard communication synthesis target- ing a refined regular distributed register architecture, named RDR-GRS, as a problem of simultaneous data transfer routing and scheduling for global interconnect resource minimization. We also present an innovative algo- rithm with regard of both spatial and temporal perspectives. It features both a concentration-oriented path router gathering wire-sharable data transfers and a channel-based time scheduler resolving contentions for wires in a channel, which are in spatial and temporal domain, respectively. The ex- perimental results show that the proposed algorithm can significantly out- perform existing related works.
September 10, 2010
We study the dimension spectrum of sofic system with the potential is matrix-valued. For positive matrix and finite-coordinate dependent matrix potential, we set up the entropy spectrum by constructing the quasi-Bernoulli measure and the cut-off method is applied to deal with the infinite-coordinate dependent case. We extend this method to non- negative matrix and give a series of examples of the sofic-affine set on which we can compute the spectrum concretely.
Fig. 10 presents a chip photograph of this paper and its summary. The technology used is a 0.18-μm complementary metal–oxide–semiconductor (CMOS) with a supply voltage of 1.8 V. The BIST circuit area is 15% of the SSCG, which includes the DFFs and phase-shift detector of the MPD but does not include the accumulator or other digital circuits. The BIST is operated at 20 MHz, which is the same as the reference clock frequency. The SSCG is a fractional-N PLL with a ten-phase 1.2-GHz VCO, a third-order loop filter, and a MASH-111 SDM to meet the SATA-III specification. In total, 10 4 data outputs by the phase-shift detector are recorded by a logic analyzer.