Method for adaptive forward power control for spread-spectrum communications

• US 6,816,473 B2
• Filed: 02/21/2001
• Issued: 11/09/2004
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Lomp, Gary R., Ozluturk, Fatih M., Kowalski, John
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/791,025
• Publication Number:
  US 20020034167A1
• Time in Patent Office: 1,357 Days
• Field of Search: 370/317, 370/318, 370/328, 370/335, 370/342, 375/130, 375/140, 375/141, 375/146, 375/147, 455/522, 455/67.11, 455/68, 455/69, 455/70, 455/115.1, 455/115.3
• US Class Current: 370/335
• CPC Class Codes: G06F 13/374 using a self-select method with individual priority code comparator
• CPC Class Codes: H03H 17/0226 comprising look-up tables
• CPC Class Codes: H03H 17/06 Non-recursive filters
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70753 Partial phase search
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70755 Setting of lock conditions, e.g. threshold
• CPC Class Codes: H04B 1/70758 Multimode search, i.e. using multiple search strategies
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/711 the interference being multi-path interference
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/70707 : Efficiency-related aspects
• CPC Class Codes: H04B 2201/7071 : with dynamic control of receiver resources
• CPC Class Codes: H04B 7/2637 : for logical channel control
• CPC Class Codes: H04B 7/264 : for data rate control
• CPC Class Codes: H04J 13/00 : Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/10 : Code generation
• CPC Class Codes: H04J 13/12 : Generation of orthogonal codes
• CPC Class Codes: H04J 13/16 : Code allocation
• CPC Class Codes: H04J 2013/0037 : Multilevel codes
• CPC Class Codes: H04L 1/0001 : Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/004 : by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/0042 : Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape H04L1/0067 takes precedence
• CPC Class Codes: H04L 1/0047 : Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/0054 : Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0059 : Convolutional codes
• CPC Class Codes: H04L 2027/003 : at baseband only
• CPC Class Codes: H04L 2027/0053 : Closed loops
• CPC Class Codes: H04L 25/0212 : of impulse response
• CPC Class Codes: H04L 27/206 : using a pair of orthogonal carriers, e.g. quadrature carriers
• CPC Class Codes: H04L 27/2332 : using a non-coherent carrier
• CPC Class Codes: H04L 5/1446 : of transmission speed
• CPC Class Codes: H04N 1/00912 : Arrangements for controlling a still picture apparatus or components thereof not otherwise provided for
• CPC Class Codes: H04N 1/3333 : during transmission, input or output of the picture signal; within a single document or page
• CPC Class Codes: H04N 2201/3335 : Speed or rate
• CPC Class Codes: H04W 52/04 : TPC
• CPC Class Codes: H04W 52/08 : Closed loop power control
• CPC Class Codes: H04W 52/143 : Downlink power control
• CPC Class Codes: H04W 52/146 : Uplink power control
• CPC Class Codes: H04W 52/24 : using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/241 : taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/245 : taking into account received signal strength
• CPC Class Codes: H04W 52/247 : where the output power of a terminal is based on a path parameter sent by another terminal
• CPC Class Codes: H04W 52/26 : using transmission rate or quality of service QoS [Quality of Service]
• CPC Class Codes: H04W 52/262 : taking into account adaptive modulation and coding [AMC] scheme AMC per se H04L1/0001
• CPC Class Codes: H04W 52/322 : Power control of broadcast channels
• CPC Class Codes: H04W 52/325 : Power control of control or pilot channels
• CPC Class Codes: H04W 52/343 : taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 : distributing total power among users or channels
• CPC Class Codes: H04W 52/36 : with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/367 : Power values between minimum and maximum limits, e.g. dynamic range
• CPC Class Codes: H04W 52/44 : in connection with interruption of transmission
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 52/52 : using AGC [Automatic Gain Control] circuits or amplifiers
• CPC Class Codes: H04W 52/54 : Signalisation aspects of the TPC commands, e.g. frame structure
• CPC Class Codes: H04W 52/60 : using different transmission rates for TPC commands

Abstract

A code-division-multiple-access (CDMA) system employing spread-spectrum modulation. The CDMA system has a base station (BS), and a plurality of subscriber units. The signals transmitted between the base station and subscriber unit use spread-spectrum modulation. The improvement method for adaptive forward power control (APC) from a base station (BS) to a subscriber unit (SU), comprises the steps of sending from the base station, using spread-spectrum modulation, a BS-spreading code on a forward channel. The subscriber unit despreads the BS-spreading code on the forward channel as a despread signal, determines a first power level P_d which includes power of the despread signal plus noise and a second power level P_N, which includes despread-noise power. The subscriber unit determines a first error signal e₁, from the first power level P_d, the second power level P_N, and a required signal-to-noise ratio SNR_REQ for service type, and a second error signal e₂, from a measure of total received power P_r and an automatic gain control (AGC) set point P_o. The subscriber unit forms a combined error signal from the first error signal e₁, the second error signal e₂, a first weight a₁ and a second weight a₂, and hard limits the combined error signal to form a single APC bit. The APC bit is transmitted to the base station. In response to the APC bit, the base station adjusts transmitter power to the subscriber unit.

Claims

1. An improvement method for adaptive forward control of power (APC) from a base station (BS) to a subscriber unit (SU), comprising the steps of:

(a) sending, from the base station to the subscriber unit, using spread-spectrum modulation, a BS-spreading code on a forward channel;

(b) despreading, at the subscriber unit, the BS-spreading code on the forward channel as a despread signal;

(c) determining, at the subscriber unit, a first power level P_d from the despread signal, whereby the first power level P_d includes power of the despread signal plus noise;

(d) determining, at the subscriber unit, a second power level P_N, whereby the second power level includes power of the despread signal minus noise;

(e) determining, at the subscriber unit, a first error signal e₁, from the first power level P_d, the second power level P_N, and a required signal-to-noise ratio SNR_REQ for service type;

(f) determining, at the subscriber unit, a second error signal e₂, from a measure of total received power P_r and an automatic gain control (AGC) set point P_o;

(g) forming, at the subscriber unit, a combined error signal from the first error signal e₁, the second error signal e₂, a first weight a₁ and a second weight a₂, with the first weight a₁ and the second weight a₂, chosen for each service type;

(h) hard limiting, at the subscriber unit, the combined error signal to form a single APC bit;

(i) transmitting, from the subscriber unit, the APC bit to the base station;

(j) receiving the APC bit at the base station; and

(k) adjusting, in response to the APC bit, at the base station, transmitter power to the subscriber unit.

2. The improvement as set forth in claim 1, with step (e) further including the step of determining, at the subscriber unit, the first error signal e₁ according to e₁=P_d−

(1+SNR_REQ)P_N, with step (f) further including the step of determining, at the subscriber unit, the second error signal e₂ according to e₂=P_r−

P_o.

3. The improvement as set forth in claim 2, with step (g) further including the step of forming, at the subscriber unit, the combined error signal according to a₁e₁+a₂e₂.

4. The improvement as set forth in claim 1, 2, or 3, further including the step of repeating steps (a) through (k).

5. An improvement method for adaptive forward control of power (APC) from a base station (BS) to a subscriber unit (SU), comprising the steps of:

(a) sending, from the base station to the subscriber unit, using spread-spectrum modulation, a BS-spreading code on a forward channel;

(b) despreading, at the subscriber unit, the BS-spreading code on the forward channel as a despread signal;

(c) determining, at the subscriber unit, a first power level P_d from the despread signal, whereby the first power level P_d includes power of the despread signal plus noise;

(d) determining, at the subscriber unit, a second power level P_N, whereby the second power level P_N includes power of the despread signal minus noise;

(e) determining, at the subscriber unit, a first error signal e₁, from the first power level P_d, the second power level P_N, and a required signal-to-noise ratio SNR_REQ for service type;

(f) determining, at the subscriber unit, a second error signal e₂, from a measure of total received power P_r and an automatic gain control (AGC) set point P_o;

(g) forming, at the subscriber unit, a combined error signal from the first error signal e₁, the second error signal e₂, a first weight a₁ and a second weight a₂, with the first weight a₁ and the second weight a₂, chosen for each service type;

(h) converting, at the subscriber unit, the combined error signal to form an APC word having at least two bits;

(i) transmitting, from the subscriber unit, the APC word to the base station;

(j) receiving the APC word at the base station; and

(k) adjusting, in response to the APC word, at the base station, transmitter power to the subscriber unit.

6. The improvement as set forth in claim 5, with step (e) further including the step of determining, at the subscriber unit, the first error signal e₁ according to e₁=P_d−

(1+SNR_REQ)P_N, with step (f) further including the step of determining, at the subscriber unit, the second error signal e₂ according to e₂=P_r−

P_o.

7. The improvement as set forth in claim 6, with step (g) further including the step of forming, at the subscriber unit, the combined error signal according to a₁e₁+a₂e₂.

8. The improvement as set forth in claim 5, 6, or 7, further including the step of repeating steps (a) through (k).