Wireless asymmetric local loop (WASL) communication

• US 6,377,562 B1
• Filed: 11/18/1997
• Issued: 04/23/2002
• Est. Priority Date: 11/18/1997
• Status: Expired due to Term

• Current Assignee: Verizon Patent and Licensing Incorporated (Verizon Communications Inc.)
• Original Assignee: Bell Atlantic Network Services, Inc. (Verizon Communications Inc.)
• Inventors: Schneider, Allan
• Primary Examiner(s): VU, HUY DUY
• Application Number:
  US08/972,250
• Time in Patent Office: 1,617 Days
• Field of Search: 370/310, 370/321, 370/328, 370/330, 370/329, 370/431, 370/436, 370/468, 370/478, 370/480, 370/483, 370/482, 370/485, 375/298, 455/452
• US Class Current: 370/330
• CPC Class Codes: H04J 3/1682 Allocation of channels according to the instantaneous demands of the users, e.g. concentrated multiplexers, statistical multiplexers
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 74/00 Wireless channel access
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A wireless, cellular radio link is provided from a base station to a plurality of subscriber stations within a cell reception area. Information data, which may be of textual, video or other format, are communicated asymmetrically as high bandwidth transmissions in the downstream direction to the users while low upstream bandwidth is provided to permit users to request the data or to provide return radio link condition information. Buffers associated with respective subscribers collect requested data from information providers for transmission by the base station in a statistical time division multiplexed (STDM) fashion, whereby each subscriber may be assigned a minimum transmission time interval during which data will be transferred from the associated buffer. Controlled logical token passing governs a variable token interval during which data transmission for each buffer is permitted in turn. Data fed from the buffers are combined in successive time intervals to form a data stream having a bit rate that can vary from interval to interval. The data stream is output as radio signals from a radio tower, each subscriber being equipped to receive that portion of the stream with which it is identified.

Claims

1. In a wireless asymmetric local loop (WASL) communication system for concurrent wireless transmission of broadband data signals individually to a plurality of users and reception of lower rate data signals from said users, a base station comprising:

a plurality of input buffers, each associated with one of said users;

a statistical time division multiplexer connected to said plurality of buffers for multiplexing data received from said buffers into a common data stream;

a frequency division multiplexer connected to receive said common data stream for modulating data thereof for each of said buffers to a respective subcarrier frequency; and

an output transmitter connected to said frequency division multiplexer.

2. A base station as recited in claim 1, wherein said output transmitter comprises:

a converter for upconverting the frequency of the modulated data;

an amplifier having an input connected to said converter and an output;

a band pass filter having an input connected to the output of said amplifier and an output; and

an antenna connected to the output of said band pass filter for transmitting data received therefrom.

3. A base station as recited in claim 1, wherein each of said input buffers has an input for receiving data from an information provider in response to a request from the associated user.

4. A base station as recited in claim 1, wherein said statistical time division multiplexer is connected to each of said input buffers to receive data therefrom in a token time interval of a repeatable time sequence for all buffers, the time duration for each buffer in said sequence being variable.

5. A base station as recited in claim 4, wherein said time division multiplexer is connected to a channel probe signal generator to receive channel probe signals therefrom, said received channel probe signals combined with received buffer data in said multiplexer.

6. A base station as recited in claim 4, wherein said time division multiplexer has an input for receiving feedback signals indicative of quality of service for a user.

7. A base station as recited in claim 6, wherein said feedback signals are indicative of channel transmission quality.

8. A base station as recited in claim 6, wherein said feedback signals are indicative of bit error rate in transmission.

9. A base station as recited in claim 6, wherein said frequency division multiplexer comprises a quadrature amplitude modulation (QAM) modulator of variable symbol size for each respective buffer, said frequency division multiplexer having an input for receiving said feedback signals.

10. A base station as recited in claim 9, further comprising:

a demultiplexer having an input to data recovered from said lower rate data signals received from said users; and

a quality of service processor having at least one input connected to said demultiplexer and an output connected for supplying said feedback signals to said statistical time division multiplexer and to said frequency division multiplexer.

11. A base station as recited in claim 1, wherein said statistical time division multiplexer comprises:

a commutator connected to each of said buffers to pass data from the respective buffer only during the corresponding token time interval of said sequence;

a token controller for said commutator; and

a data buffer connected to receive the buffer data.

12. In a wireless asymmetric local loop (WASL) communication system, a method for wireless transmission of broadband data concurrently and individually to a plurality of users, said method comprising the steps of:

individually buffering data from at least one information provider for each of said plurality of users;

statistically time division multiplexing the data buffered in said buffering step for each user in a repeating sequence to a common data stream;

modulating the data for each user from said common stream to a respective subcarrier frequency; and

concurrently transmitting the frequency modulated data obtained in said modulating step to each user.

13. A method as recited in claim 12, wherein said multiplexing step comprises:

setting a minimum transmission time interval for each user in said sequence in accordance with a respective preset time interval level; and

applying a logical token ring protocol to establish a variable token transmission time interval in said sequence for each buffer that is equal to or greater than the respective minimum transmission time interval in said setting step.

14. A method as recited in claim 13, further comprising the step of detecting quality of transmission and bit error rate conditions during each token transmission time interval, and wherein said multiplexing step further comprises:

setting a transmission bit rate for transmission of data from each buffer in accordance with a preset bit rate level for each respective user; and

adjusting said transmission bit rate in response to a change in the detected conditions.

15. A method as recited in claim 13, wherein said multiplexing step further comprises:

defining a constant target token rotation time (TTRT) interval within which each complete sequence of token transmission time intervals occurs, whereby a latency period between successive possible data transfers from any respective buffer is limited to a set time span.

16. A method as recited in claim 14, wherein said multiplexing step further comprises:

determining a level of data transmission activity during each said sequence; and

setting a token transmission time interval for a particular user greater than the corresponding minimum transmission time interval for said particular user in response to a determination of relative transmission inactivity by other users in said determining step; and

adjusting the token transmission time interval for said particular user in response to said change in conditions detected in said detecting step for said particular user.

17. A method as recited in claim 12, wherein said modulating step comprises:

dividing a frequency spectrum into subcarrier frequencies respectively associated with said users; and

quadrature amplitude modulating (QAM) each of said subcarrier frequencies with the data from the common data stream for the respective user.

18. A method as recited in claim 17, further comprising the step of detecting quality of transmission and bit error rate conditions for each user during transmission, and wherein said modulating step further comprises:

setting a QAM symbol level for each respective user; and

adjusting said QAM symbol level in response to a change in the detected conditions.