The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Unique word - orthogonal frequency division multiplexing (UW-OFDM) is a novel OFDM concept that uses deterministic sequences, which we call unique words, as guard intervals instead of the conventional cyclic prefixes. Since unique words represent known sequences, they can advantageously be used for synchronization, channel estimation, but also for improving the bit error ratio (BER) behavior of a...
Multiple-input multiple-output (MIMO) antennas combined with orthogonal frequency division multiplexing (OFDM) are very attractive for high data rate communications. However, MIMO-OFDM systems are very vulnerable to time selective fading as channel time variation destroys the orthogonality among subcarriers, causing serious intercarrier interference (ICI). In this paper, we employ optimal frequency...
Narrowband communications over power lines has been in use for automatic meter reading (AMR) of electric, gas, and water meters. The major hurdle in the widespread use of this medium is the time varying nature of the channel and impairments such as the presence of colored background noise and large impulse noises in time and frequency domains. In this paper, we model the extremely noisy channel environment...
This paper discusses the design and analysis of post coded OFDM (PC-OFDM) systems. Coded or precoded OFDM systems are generally employed to overcome the symbol recovery problem in uncoded OFDM systems. We show that PCOFDM systems are a special case of precoded OFDM systems that offer advantageous complexity-performance trade-offs. In particular, PC-OFDM systems introduce frequency diversity by manipulating...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading...
Effects of improved channel estimation are studied for a proposed IEEE 802.11n OFDM MIMO system. Three channel estimation methods are considered: maximum likelihood (ML), time-domain truncation (TDT) and model-based (MB). TDT and MB are particularly useful when the channel delay spread is short. For an MMSE receiver, MB shows a 1-2.5 dB improvement over ML on the packet error rate performance for...
In this paper, we consider a new channel probing scheme for opportunistic scheduling in the uplink of orthogonal frequency division multiplexing (OFDM)-based wireless systems. To reduce signaling overhead for the probing, we consider a two-step channel probing process; called pre-probing and mainprobing. Good subchannels are first estimated through the pre-probing process using a probing signal transmitted...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.