摘要:
A modem (12) including a least-significant bit convolutional coding scheme is disclosed. In the transmit side of the modem (12), an encoder (28) is included, within which convolutional coders (35I, 35Q) are used to each encode one bit of each symbol applied to a phase and amplitude modulation constellation, preferably the least significant bits, such that the encoded bits select one of a plurality of sub-constellations in the modulated signal. Each of the coders (35, 35′) are arranged as finite state machines, of either thirty-two or sixty-four states. The minimum Hamming distance (dfree) provided by the codes is four, such that the resulting coding gain of the modem is improved over conventional encoding schemes.
摘要:
A linecard codec (250) eliminates limitations of companded code disclosed which increases data rates over a public switched telephone network. The network links a plurality of subscribers and services providers through a central office facility (25) which includes at least one digital backplane (150). The codec (250) comprises an analog interface (152) to the network and a converter (258) coupled to the analog interface and configured to convert analog signals from subscribers to linear coded data (259). A RAM table (262) is used to map the linear coded data (259) to a predetermined coding scheme based on the values stored in the RAM table (262). The RAM table (262) stores mapping values that determine a mapping function between data transmitted by a service provider on the digital backplane (150) and data transmitted to a subscriber.
摘要:
A communications device (100) with an extended filter (74) provides more bandwidth for V.34, V.90 and other data communications protocols. The device (100) permits voice and data communications over the same twisted pair connection (22) to a central office facility (35) and allows an increased data rate between a subscriber (15) and the central office linecard (50). A variable frequency filter (74) capable of switching between “voice” mode and “data” mode is used. In “data” mode, the bandwidth of filter (74) is extend to provide more bandwidth which can be utilized to transfer data. A line monitoring mechanism (102) is provided which monitors the PCM data flowing over a digital backplane (60) as well as requests from a subscriber for an increased data rate connection. A micro-controller (104) can be provided to adjust the bandwidth of the filter (74) and cause it to enter “data” mode.
摘要:
A trellis shaping method is described that may be used for suppressing DC components and/or Nyquist frequency components from the outputs of a PCM (56K) modem. The technique is based on convolutional codes. The code is generated through the use of a Viterbi decoder. Data bits are mapped for transmission into a set of n magnitudes and (n−k) sign bits s. The sign bits s are passed through (HT)−1 to get preliminary sing bits t=s (HT)−1 of size n. (HT)−1 is a matrix of size (n−k) by n which represents the left inverse of the syndrome-former matrix HT of convolutional code c=b G, defined so that G HT=0. The convolutional code is then added to sign bits t through an XOR operation to give final sign bits s (HT)−1+b G. After transmission, the final sign bits are passed through HT to give an output of (s (HT)−1+b G) (HT))=s, for recovery of the data bits.
摘要翻译:描述了可用于从PCM(56K)调制解调器的输出抑制DC分量和/或奈奎斯特频率分量的网格整形方法。 该技术基于卷积码。 该代码通过使用维特比解码器生成。 映射数据位以传输到一组n个幅度和(n-k)个符号位。 符号位通过(HT)-1,以获得大小为n的初步字位t = s(HT)-1。 (HT)-1是大小(n-k)乘以n的矩阵,其表示卷积码c = b G的综合征 - 形成矩阵HT的左倒数,使得G HT = 0。 然后通过XOR操作将卷积码添加到符号位t,以得到最终符号位s(HT)-1 + b G。传输后,最终符号位通过HT,输出(s(HT) -1 + b G)(HT))= s,用于恢复数据位。
摘要:
A wireless communication system (10). The system comprises transmitter circuitry (BST1) comprising circuitry for transmitting a plurality of frames to a receiver in a first cell (Cell 1). Each of the plurality of frames comprises a bit group (22), and the bit group uniquely distinguishes the first cell from a second cell (Cell 2) adjacent the first cell. The transmitter circuitry further comprises circuitry (54) for inserting a bit sequence into the bit group. The bit sequence is selected from a plurality of bit sequences (S1-SK) such that successive transmissions by the transmitter circuitry comprise a cycle of successive ones of the plurality of bit sequences.
摘要:
In one form of the invention, a process of sending real-time information from a sender computer (103) to a receiver computer (105) coupled to the sender computer (103) by a packet network (100) wherein packets (111,113) sometimes become lost, includes steps of directing (441) packets (111) containing the real-time information from the sender computer (103) by at least one path (119) in the packet network (100) to the receiver computer (105), and directing packets (113) containing information dependent on the real-time information from the sender computer (103) by at least one path diversity path (117) in the packet network (100) to the same receiver computer (105). Other forms of the invention encompass other processes, improved packets and packet ensembles (111,113), integrated circuits (610), chipsets (DSP 1721, MCU), computer cards (1651), information storage articles (1511,1611), systems, computers (103,105), gateways (191,193), routers (131,133), cellular telephone handsets (181,189), wireless base stations (183,187), appliances (1721,1731,1741), and packet networks (100), and other forms as disclosed and claimed.
摘要:
An apparatus and method for transmitting and receiving a bit stream. On the transmission side, coded bits (Y.sub.t) and an interleaved version of the coded bits (X.sub.t) are separately modulated and transmitted. On the reception side, a priori output probabilities produced by a probability generator (34) are combined (112) and then input to a SISO decoder (111). Combined a posteriori output probabilities (115) produced by the SISO decoder are split (113) and then fed back to the probability generator.
摘要:
A wireless communication system (10). The system comprises transmitter circuitry (BST1) comprising circuitry for transmitting a plurality of frames to a receiver in a first cell (Cell 1). Each of the plurality of frames comprises a bit group (22), and the bit group uniquely distinguishes the first cell from a second cell (Cell 2) adjacent the first cell. The transmitter circuitry further comprises circuitry (54) for inserting a bit sequence into the bit group. The bit sequence is selected from a plurality of bit sequences (S1-SK) such that successive transmissions by the transmitter circuitry comprise a cycle of successive ones of the plurality of bit sequences.
摘要:
A wireless communication network (10) includes a wireless transmitter having a plurality of antennas (AT11, AT12). The transmitter includes for each of a plurality of different user channels (Dn), circuitry (22n) for providing a plurality of groups of symbols in a first symbol group sequence (D1n). Each of the plurality of different user channels includes circuitry (241n) for forming a first modulated symbol group sequence for the user channel by modulating the symbols in the first symbol group sequence with a unique code that corresponds to the user channel and distinguishes the user channel from each other of the plurality of different user channels and circuitry (261) for combining the first modulated symbol group sequences for transmission by a first antenna (AT11). Each of the plurality of different user channels includes circuitry (22n) for forming a second symbol group sequence (D2n) by time reversing symbols in at least some of the groups of symbols.
摘要:
An apparatus and method for transmitting and receiving a bit stream. On the transmission side, coded bits (Y.sub.t) and an interleaved version of the coded bits (X.sub.t) are separately modulated and transmitted. On the reception side, a priori output probabilities produced by a probability generator (34) are combined (112) and then input to a SISO decoder (111). Combined a posteriori output probabilities (115) produced by the SISO decoder are split (113) and then fed back to the probability generator.