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The creation of Ultra-Wideband (UWB) radio platform has allowed the development of high bit-rate Wireless-USB offering High Definition video streaming. Quadrature Phase Shift Keying (QPSK) and Dual Carrier Modulation (DCM) are the current modulation schemes used for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the ECMA-368 defined UWB radio platform. ECMA-368 offers up to 480...
We analyze the fundamental limits of key generation and describe an implementation based on error correcting codes. We show that key extraction based on channel coefficients significantly outperforms key extraction based on received signal strength indicators (RSSI). The development in this paper is based on an IEEE 802.11a orthogonal frequency-division multiplexing (OFDM) model and We demonstrate...
In this paper, we propose an iteration scheme for the virtual layered space frequency communication architecture. The architecture enables the decoding of the transmitted orthogonal frequency division multiplexing (OFDM)-QPSK signals even if the number of spatial multiplexed layers is twice that of receiving antennas over multipath fading channels. In the proposed iteration scheme, the MAP decoder...
In this research paper, we carry out comparative performance evaluation of Low Density Parity- Check (LDPC) coded and Turbo coded orthogonal frequency division multiplexing (OFDM) systems by varying a number of parameters/factors including channel types, data block size, and number of decoding iterations. OFDM possesses the ability to counter sever channel conditions if coded with a suitable error...
This paper describes low power architecture by using a dynamic wordlength technique in wireless orthogonal frequency division multiplexing (OFDM) system. The number of wordlength in digital signal processing (DSP) has to be carefully determined because wordlength affects system performance and hardware cost. Dynamic wordlength technique is applied to a fast Fourier transform (FFT) processor and a...
In this paper, we propose a novel transmit signal structure for OFDM (orthogonal frequency division multiplexing). Instead of the conventional cyclic prefix (CP), we use a deterministic sequence, which we call unique word (UW), as guard interval. We show how unique words, which are already well investigated for single carrier systems with frequency domain equalization (SC/FDE), can also be introduced...
This paper investigates the transmission in time dispersive channels of Spectrally Efficient Frequency Division Multiplexed (SEFDM) signals, where carrier orthogonality is intentionally violated in order to increase bandwidth efficiency. Sufficient statistics of the transmitted SEFDM signal can be obtained by projecting the received signal onto an orthonormal base generated at the receiver using an...
This paper proposes an OFDM based transmission scheme for asynchronous amplify-and-forward cooperative systems with two relay nodes over frequency-selective channels. To combat the inter-symbol interference from multi-path fading and timing errors, the cyclic prefix (CP) is used at both the source node and relay nodes. Unlike using IDFT and DFT modulation for two consecutive OFDM blocks respectively,...
Single-carrier frequency-division multiple-access (SC-FDMA) has been adopted in the uplink of the LTE standard due to its lower peak-to-average-power ratio (PAPR) compared to orthogonal frequency-division multiple access (OFDMA). Recent activities in the LTE-advanced (LTE-A) standardization have focused on effective uplink transmit diversity schemes with low PAPR but without considering the performance...
This work considers the problem of channel estimation in the context of non-binary-LDPC-coded OFDM transmission over doubly-selective multipath channels. The potential of channel encoding is exploited to derive an iterative Wiener-filter-based estimation method using both time and frequency autocorrelation of the channel. The proposed algorithm can use either the soft information or the hard decisions...
The performance of a space-time block coded orthogonal frequency-division multiplexing (STBC-OFDM) system often relies on the assumption of quasi-static channels. For the time-varying multipath channel, co-channel interference (CCI) and inter-carrier interference (ICI) occur and performance degrades seriously. In this paper, we propose an iterative interference cancellation scheme to reduce both CCI...
We investigate the case of Block Turbo Codes (BTCs) combined with Orthogonal Frequency Division Multiplexing (OFDM) technique for Unmanned Aerial Vehicles (UAVs) highspeed data link. Considering the UAV channel with time-varying and multipath fast fading characteristics, a 3-path UAV channel model is developed, which can be readily implemented under simulation condition. Two typical communication...
Dual Carrier Modulation (DCM) is currently used as the higher data rate modulation scheme for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the ECMA-368 defined Ultra-Wideband (UWB) radio platform. ECMA-368 has been chosen as the physical radio platform for many systems including Wireless USB (W-USB), Bluetooth 3.0 and Wireless HDMI; hence ECMA-368 is an important issue to consumer...
Digital Radio Mondiale (DRM) is a new digital radio broadcasting system for the frequency bands below 30 MHz. High quality audio and data transmission is achieved by adopting COFDM modulation combined with a multilevel coding scheme, which has high resistance to multipath fading and interference. In this paper, we present the algorithm design and implementation of a low-power consumption portable...
In this paper, we analysis the receiver of orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels where the multipath delay exceeds the guard interval duration and propose a novel receiver scheme. The proposed receiver consists of the Inter Symbol Interference (ISI) canceller and the turbo equalizer. At each iteration, the proposed turbo equalization algorithm...
The probability density function (PDF) of the intercell interference for downlink cellular orthogonal frequency division multiple access networks under log-normal shadowing and multipath Rayleigh fading is derived. The derived PDF is observed to highly deviate from the Gaussian distribution, especially at moderate to small network loads. Based on the derived inter-cell interference statistics, the...
To deal with the multi-path delay spread in non- line-of-sight (NLOS) environments, single-carrier frequency- domain equalization (SC-FDE), a.k.a., single-carrier block transmission (SCBT), is thought to be an effective alternative of orthogonal frequency division multiplexing (OFDM). On the other hand, the low-density parity-check (LDPC) coding is considered as the high-performance channel coding...
This paper presents a practical low-density parity-check (LDPC) coded OFDM system designed for the underwater acoustic channel with its attendant multipath channel and large Doppler shift. The Doppler shift and channel state information (CSI) are assumed unavailable to both to the transmitter and the receiver. Due to the slow speed of sound in water, even small platform motions can affect the performance...
It has been shown that relaying systems can offer spatial and multipath diversity in amplify-and-forward (AF) relay-assisted transmission over frequency-selective fading channels when trellis coded modulation (TCM) is applied as an outer code. However, the price for such advantages is the high decoding complexity. To overcome this disadvantage, the technique of subcarrier grouping is applied for orthogonal...
Fourth generation broadband wireless access systems based on OFDMA/OFDM techniques operate in point-to-multipoint (PMP) configuration so that conventional cellular planning methods can be used for network design. As an alternative planning method fractional frequency reuse (FFR) strategy has been recently proposed for OFDMA/OFDM cellular systems such as WiMAX. For what concerns the determination of...
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