What is bit loading in OFDM?
A new approach to loading for orthogonal frequency division multiplexing (OFDM) system is proposed, this bit-loading algorithm assigns bits to different subchannels in order to minimize the transmit energy. In this way the algorithm is efficient while calculation is less complex.
What is bit loading?
In adaptive Bit-loading the number of bits that can be transmitted in each subcarrier is determined by the SNR on the subcarrier. Channel utilization and date rate can be significantly improved by using adaptive bit loading.
What is bit and power loading?
Bit and power loading algorithms can be generally categorized into two main classes, i.e., algorithms whose objective is to maximize the achievable system margin, margin maximization (MM), [4], [5] and algorithms whose objective is to maximize the achievable data rate, rate maximization (RM), [1], [6].
What is bit loading in ADSL?
~ Bit Loading If the SNR is weak/weaker at a particular frequency range, then not as many bits can be carried by the tone. Each 3dB of SNR equates to 1 bit (of data), A minimum of 2 bits per bin is needed for the tone to be usable for ADSL1 (6dB) ADSL2 and ADSL 2+ support single bit tones (3dB).
What are the advantages of OFDM?
Immunity to selective fading: One of the main advantages of OFDM is that is more resistant to frequency selective fading than single carrier systems because it divides the overall channel into multiple narrowband signals that are affected individually as flat fading sub-channels.
What is G DMT mode?
992.1 (better known as G. dmt) is an ITU standard for ADSL using discrete multitone modulation (DMT). G. dmt full-rate ADSL expands the usable bandwidth of existing copper telephone lines, delivering high-speed data communications at rates up to 8 Mbit/s downstream and 1.3 Mbit/s upstream.
What frequency does ADSL use?
With commonly deployed ADSL over POTS (Annex A), the band from 26.075 kHz to 137.825 kHz is used for upstream communication, while 138–1104 kHz is used for downstream communication. Under the usual DMT scheme, each of these is further divided into smaller frequency channels of 4.3125 kHz.
Why orthogonality is important in OFDM?
In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel. This maintains total data rates similar to conventional single-carrier modulation schemes in the same bandwidth.