Variable spacing pulse position modulation for ultra-wideband communication links

• US 20040057500A1
• Filed: 09/23/2002
• Published: 03/25/2004
• Est. Priority Date: 09/23/2002
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Calin, Doru, Balachandran, Krishna, Ji, Tingfang, Kang, Joseph H.
• Granted Patent: US 7,082,153 B2
• Time in Patent Office: Days
• US Class Current: 375/138
• CPC Class Codes: H04B 1/7176 Data mapping, e.g. modulation
• CPC Class Codes: H04B 2001/6908 using time hopping
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

Methods and systems for generating a variable spacing pulse position modulated (VSPPM) signal for transmission across an ultra-wideband communications channel. The variable pulse position modulated spread spectrum signal is created by encoding every M input data bits from an input data stream into a symbol consisting of N_c chips. Each chip is divided into 2^M sub-chips and each sub-chip is further divided into N_p time slots. A pulse is transmitted for each chip in the symbol. During each chip period, the pulse is placed in the sub-chip corresponding to the binary M-tuple (or symbol) value. A time hopping code sequence consisting of N_c elements with a one-to-one chip association is then applied to each symbol so that the position of each pulse is shifted to the appropriate time slot that corresponds to the time hopping code value.

Claims

1. A method for modulating a communications signal across a communications channel, comprising:

receiving a plurality of input data bits, each input data bit having a first value or a second value;

receiving at least one time hopping code sequence comprising N_p elements, each element having a code value;

encoding a set of M input data bits into a symbol having a value in the range of 0 to (2^M−

1), the symbol comprising N_c chips, each chip consisting of 2^M sub-chips, wherein each of the 2^M sub-chips comprises N_p time slots;

generating a pulse in one of the 2^M sub-chips that corresponds to the symbol value;

associating at least one time hopping code sequence with each symbol value;

associating each code value in the at least one time hopping code sequence with at least one chip in the symbol; and

shifting the position of the pulse within the sub-chip in each chip to at least one of the N_p time slots, wherein the time slot corresponds to the code value associated with that chip.

2. The method of claim 1, wherein receiving at least one time hopping code sequence comprises:

receiving 2^M time hopping code sequences, each comprising N_c elements, and each element having a code value in the range of 0 to (N_p−

1);

associating at least one of the 2^M time hopping code sequence with each of the symbol values; and

applying the time hopping code sequence associated with the symbol value to each symbol having that particular symbol value.

3. The method of claim 1, wherein the time hopping code sequence is a pseudorandom sequence.

4. The method of claim 1, wherein the time hopping code sequence is are orthogonal sequence.

5. The method of claim 1, wherein the value of M is 1.

6. The method of claim 1, wherein the communication channel is a wireless radio channel.

7. An ultra-wideband (UWB) transmitter operable for transmitting a pulse position a spread spectrum signal over a communications channel, comprising:

a spread spectrum encoder operable for;

receiving at least one time hopping code sequence comprising N_c elements, each element consisting of a code value;

receiving a plurality of input data comprising a plurality of binary bits; and

applying the at least one time hopping code sequence to encode M binary bits into symbols with values in the range of 0 to (2^M−

1), each symbol consisting of a number of predefined chips, N_c, each chip consisting of 2^M sub-chips, and each sub-chip consisting of N_p time slots;

associating at least one time hopping code sequence with each symbol value; and

associating at least one code value with each sub-chip in each chip in the symbol;

a time-hopping code generator connected to the spread spectrum encoder for generating the least one time hopping code sequence;

a pulse generator for generating a plurality of pulses; and

a pulse position modulator for modulating the plurality of pulses generated by the pulse generator.

8. The transmitter of claim 7, wherein modulating the plurality of pulses generated by the pulse generator, comprises:

placing a pulse in one of the sub-chips in each chip of a symbol, where the sub-chip corresponds to the particular symbol value; and

shifting the position of the pulse within the sub-chip to the time slot corresponding to the code value associated with that particular chip.

9. The transmitter of claim 7, wherein only one time hopping code sequence is applied to encode M binary bits into a symbol.

10. The transmitter of claim 7, wherein the time hopping code sequences are pseudorandom code sequences.

11. The transmitter of claim 7, wherein the time hopping code sequences are orthogonal sequences.

12. The transmitter of claim 7, wherein the value of M is 1.

13. The transmitter of claim 7, further comprising an antenna for applying the modulated spread spectrum signal to the communications channel.

14. The UWB transmitter of claim 7, wherein the communications channel is a wireless radio channel.