This work presents a wideband switchless Front-End (FE) which contains a two-stage power amplifier (PA) and a two-stage low noise amplifier (LNA). The linearity of the PA is the focus of the work in the transmitter side (TX) and is improved by adopting a stacked configuration with an adaptive bias technique. The adaptive bias improves the output compression point (O1dB) by nearly 5 dBm. A driver is placed before the output stage of the PA to ensure wideband operation and higher gain. The LNA consists of two-stage single ended configurations and uses the current steering architecture to provide extended reconfigurable operation. Both LNA and PA are connected to the antenna through a passive structure called duplexer which provides optimum noise and power matching at each side with low losses and minimum area occupation. The process used for the design is TSMC’s 40nm bulk CMOS and all the simulations are post layout extracted. The design covers a 3-dB bandwidth of 11 GHz from 22.7 to 33.8 GHz and presents linearity of 18 dBm for the TX and a noise figure (NF) of 4.5 dB for the RX part with 20.7 dB gain.

This paper proposes a scalable prototype surveillance/alarm ITS (Intelligent Transportation System) for roadways safety applications over roadway environments with emphasis given in the wireless vehicular communication inside a tunnel after an emergency event. A heterogeneous hybrid vehicular wireless network consisted of IEEE 802.11b/g/e and IEEE 802.16e is being deployed inside a tunnel environment for traffic safety and surveillance reasons. Extensive measurements throughout a total length of 1km are employed to evaluate the Quality of Service in terms of throughput, packet error rate, SNR, Jitter and packet loss performance over different modulation and code rate schemes. Moreover, we also used the NARDA SRM-3006 to survey wireless channel characterization in terms of large-scale fading investigation for an irregular topology featuring the unlicensed WiMAX 5.745GHz 802.16e channel providing an overview analysis of the in-tunnel wireless communication network.

Hybrid wireless networks have been identified as a promising solution to establish communication over vehicular systems that can overcome the current and future needs for increasing public safety and efficiency. In this paper a heterogeneous hybrid vehicular wireless network consisted of IEEE 802.11b/g/e and IEEE 802.16e is being deployed inside a tunnel environment for surveillance reasons. Furthermore, we analyze the proposed vehicular wireless network architecture and provide the performance evaluation of the hybrid WiFi/WiMAX wireless network implementation during handover process after an emergency situation (fire or explosion). Moreover, we also survey through OMNeT++ simulator tool the performance of the hybrid wireless network over the handover procedure. Finally, we provide a comparison between the experimental and simulated results emphasizing on link quality metrics such as average packet end-to-end delay, SNR and throughput.

Signal-to-noise ratio (SNR) is an important parameter for adaptive orthogonal frequency division multiplexing (OFDM) systems as it serves as a standard measure of signal quality. In this work, we present a novel SNR per subcarrier estimation scheme for wireless OFDM systems in frequency selective channels. The novel scheme can operate both in time and frequency, requiring only one previously known OFDM symbol. Firstly the noise variance per subcarrier estimate is obtained using the estimated channel coefficients and a novel analysis of its estimation error is provided. The noise variance per subcarrier estimate is used to obtain the SNR per subcarrier estimate. The estimation scheme takes under consideration the frequency selectivity of the channel and the variation of the noise statistics across the OFDM subcarrier index. The estimator's performance, in means of normalized mean square error (NMSE), is evaluated through simulations on a variety of channel models and is compared with another estimation scheme. The NMSE of the proposed scheme demonstrates its ability to identify the local statistics of the noise efficiently resulting into a reliable estimator in contrast with other similar approaches.

A subharmonic injection-locked self-oscillating mixer (s-ILSOM) at 1 GHz is reported in this paper. The proposed circuit which combines both injection-locking and mixing functions is described theoretically and experimentally. In contrast to previously reported works, only one input port is required for both the RF/IF signal and the injection signal. Furthermore, the injection signal which is used to stabilize the oscillation is at a subharmonic of the oscillation frequency (fLO/4), with a power level as low as -20 dBm. Phase noise calculations and mixing characteristics are reported, indicating a noise improvement, and a high up-conversion gain for both fundamental and harmonic mixing. The circuit is implemented, using a GaAs FET, exhibiting an up-conversion gain of 13 dB, a phase noise of -93 dBc/Hz at 100 KHz offset, a P1dBof -18 dBm, an IP3 of -5 dBm, and a power consumption of 24 mW.

In this work, the performance of a novel linear interpolator scheme that uses K successive orthogonal frequency division multiplexing (OFDM) symbols is examined. The estimator collects K successive OFDM symbols to create a virtual super symbol (VSS) with K-P pilots using P pilots from each OFDM symbol. The (K - 1) middot P pilots are shifted in frequency in such way that in the VSS their distance is divided by K compared to standard symbols. Successive least squares (SLS) channel estimation through linear interpolation is performed by using more than one symbol in the LS estimator introducing the weight channel change (WCC) factor that represents the change of the wireless channel between the successive symbols used. A novel analysis deriving exact expressions for the mean square error (MSE) as a function of pilot spacing, channel statistics and WCC for an OFDM system where data subcarriers also exist before the first and after the last pilot is given. The MSE and the bit error rate (BER) of the estimator are characterized by the number and distance of the pilots, the Doppler spread and the WCC factor. Simulations show the effect of each factor on MSE and BER performance.

In this work the characteristics of the radio channel of a typical industrial environment are examined in detail by means of experimental measurements. The channel impulse response is measured at several representative positions. These measurements are then used to calculate important propagation parameters like attenuation, rms delay spread and coherence bandwidth. Furthermore, directional antennas are used to investigate the effect of directional transmission in propagation parameters. Finally, the performance of direct sequence spread spectrum (DSSS) radio transmission (in the 2.4 GHz band) is evaluated for omnidirectional and directional reception by means of bit error rate (BER) measurements at the same characterized positions

The performance of carrier frequency offset (CFO) estimators is examined when applied to Hiperlan2 modems. The performance of various estimator procedures is evaluated by means of simulation. A new estimation scheme is proposed for Hiperlan2 that takes advantage of the structure of the physical frames. Its major advantage is that the estimator operating range is extended to fulfil a worst-case scenario of CFO for Hiperlan2. A CFO correction architecture is also proposed which consists of 2 parts; a coarse CFO estimator that feeds a numerically controlled oscillator (NCO) to remove a part of CFO, and a fine CFO estimator-corrector that uses linear phase extrapolation to correct the phase shift caused by the remaining CFO.

A multicarrier transmission system is sensitive to carrier frequency offset (CFO) that produces severe inter-carrier interference (ICI). In this work a novel architecture for CFO cancellation is proposed for HIPERLAN/2 type modems. The proposed architecture consists of two parts: a coarse and a fine CFO cancellation subsystem. In the coarse subsystem an extended range correlation type time domain CFO estimation scheme is employed. Then a complex numerically controlled oscillator (CNCO) is used to reduce the main part of the CFO effects. In the fine CFO correction subsystem, a frequency-domain pilot-based estimator is proposed. The proposed scheme measures the phase drift of HIPERLAN/2 pilots in frequency domain and produces an estimation of the relative phase drift of each sample in the time-domain. The result is used to correct the remaining effects of the CFO. The proposed novel architecture is an all-digital feed-forward scheme that means no feedback to the analog front-end of the receiver is required. This fact reduces the implementation complexity.

The benefits of wireless extensions in industrial networks are well recognized as long as the integration of the wireless and fieldbus domains will be capable to offer the realtime and dependability quality of the current wired industrial networking solutions. This paper presents a study, from a performance point of view, for the possible integration of the most popular 3G and WLAN radio technologies with fieldbus technologies. A brief examination of a number of dominant wireless protocols against the basic wireless fieldbus requirements is presented. For the case study, Profibus is used, on which, the basic message cycle performance is calculated for each of the UNITS, 802.11b and HIPERLAN protocols, under different integration approaches.

Recent advances in electronic technology integration coupled with increasing needs for more services in portable communications favors the development of high performance dual-mode terminals. We present the complete architecture implementation of the GMSK/GFSK modulator/demodulator including the FIR filters design. The main features of the modulator/demodulator and the architectural implementation of FIR filters are described. The interface with ASPIS processor and A/D & D/A converters is also described in detail manner. The whole architecture of the modulator/demodulator was described by VHDL hardware language, synthesised and implemented in Xilinx environment.

The interest for small size low complexity radio systems has resulted in examination of efficient architectures for transceiver implementation. This in turn has pushed towards smaller RF subsystems and efficient digital baseband sections. An all-digital low complexity baseband receiver is presented for a DECT radio system employing the direct conversion approach. This approach permits generation of in-phase and quadrature (I/Q) signal components. We present a novel approach for the differential detector using a finite state machine approach. The symbol timing algorithm uses oversampling only during the packet synchronization word whereas the frequency offset correction algorithm operates on the symbol rate permitting corrections up to 12% of the symbol rate. The symbol timing and the frequency correction algorithms are also implemented in an all-digital fashion emphasizing low complexity realization.

A first assessment of the applicability and the tradeoffs involved in a switched (antenna) diversity approach is presented here as seen in the context of a future indoor wireless network operating in the mm-wavelength radio spectrum targeted to provide radio access to asynchronous transfer mode local area networks (ATM LAN's) and broadband integrated services digital networks (B-ISDN). Measurements conducted at 21.6 GHz are used to examine the gain variation of switched-diversity alternatives in terms of cumulative distribution functions. The performance of a two-branch post-detection code diversity combining scheme under Rayleigh fading conditions is also included for purposes of comparison. The results of our work here confirm the hypothesis that the choice of the employed antenna diversity technique in combination with the selected micro-cellular architecture have significant effects on both the throughput and the measured performance of future radio links.

A lbrst assessment of the applicability and the trade- offs involved in a switched (antenna) diversity approach is pre- sented here as seen in the context of a future indoor wireless network operating in the mm-wavelength radio spectrum tar- geted to provitde radio access to asynchronous transfer mode local area networks (ATM LAN's) and broadband integrated services digital networks (B-ISDN). Measurements conducted at 21.6 GHz are used to examine the gain variation of switched- diversity alternatives in terms of cumulative distribution func- tions. The performance of a two-branch post-detection code diversity combining scheme under Rayleigh fading conditions is also included for purposes of comparison. The results of our work here confiirm the hypothesis that the choice of the employed antenna divers,ity technique in combination with the selected micro-cellular architecture have significant effects on both the throughput and the measured performance of future radio links.