Pro-active antenna switching based on relative power

• US 6,891,909 B2
• Filed: 02/28/2001
• Issued: 05/10/2005
• Est. Priority Date: 02/28/2001
• Status: Expired due to Fees

• Current Assignee: GE Marquette Medical Systems, Inc. (General Electric Company)
• Original Assignee: GE Marquette Medical Systems, Inc. (General Electric Company)
• Inventors: Hurley, James Patrick, Hoctor, Ralph Thomas
• Primary Examiner(s): Tesfaldet, Bocure
• Assistant Examiner(s): Tran, Khanh
• Application Number:
  US09/795,541
• Publication Number:
  US 20020118780A1
• Time in Patent Office: 1,532 Days
• Field of Search: 375/267, 375/346, 375/347, 375/348, 375/349, 375/316, 455/269, 455/272, 455/277.1, 455/277.2, 455/278.1, 455/132, 455/133, 455/134, 455/135, 370/500, 370/509, 370/510, 370/512, 370/513
• US Class Current: 375/347
• CPC Class Codes: H04B 7/0811 during preamble or gap period

Abstract

A system and a method for switching antenna fields without waiting until data packets containing errors are detected. This is accomplished by monitoring the signal power for each antenna field immediately after receipt of data packets via the currently active antenna field and then switching to another antenna field having greater signal power. A communications channel is provided which has a capacity greater than that required by the data to be transmitted. This extra capacity is used to introduce time periods when no data is being transmitted. During these time periods, known bit patterns are transmitted, and the signal power during receipt of each of these blank packets is estimated for each antenna field. The receiver then switches to the most appropriate antenna field based on highest signal power (e.g., based on a weighted average for the N-th most recent sample periods) and continues to receive the transmitted data without interruption.

Claims

1. A method of wireless communication, comprising the following steps:

(a) acquiring first through N-th packets of data at a remote site;

(b) transmitting said N packets of data from an antenna at said remote site in the form of modulated signals, each modulated signal having a bit pattern dictated by the acquired data;

(c) receiving at least portions of said modulated signals of said N packets of data in first and second antenna fields;

(d) demodulating said portions of said modulated signals of said N packets of data detected in said first antenna field;

(e) after transmitting said N-th packet of data, transmitting an (N+1)-th packet from said antenna at said remote site, said (N+1)-th packet being transmitted in the form of a modulated signal having a known bit pattern not dictated by the acquired data;

(f) receiving at least a portion of said modulated signal of said (N+1)-th packet in said first antenna field;

(g) calculating the power of said modulated signal of said (N+1)-th packet from said first antenna field;

(h) after transmitting said (N+1)-th packet, transmitting an (N+2)-th packet from said antenna at said remote site, said (N+2)-th packet being transmitted in the form of a modulated signal having a known bit pattern not dictated by the acquired data;

(i) receiving at least a portion of said modulated signal of said (N+2)-th packet in said second antenna field;

(j) calculating the power of said modulated signal of said (N+2)-th packet from said second antenna field; and

(k) selecting one of said first and second antenna fields to provide detected modulated signals for demodulating subsequent to transmission of said (N+2)-th packet, the results of said selecting step being a function of the results of said calculating steps.

2. The method as recited in claim 1, wherein steps (a) through (j) are repeated at least two times, the results of said selecting step being a function of the results of all of said calculating steps.

3. The method as recited in claim 1, wherein said acquiring step comprises monitoring a patient.

4. A communications system comprising:

a transmitter for transmitting modulated signals representing a sequence of data packets followed by a sequence of blank packets every cycle;

a plurality of receive antennas; and

a receiver coupled to each of said receive antennas, wherein said receiver comprises;

an antenna switch having an output and a plurality of inputs, each of said inputs being respectively connected to receive a signal derived from a respective modulated signal output by a respective receive antenna upon receipt of a transmitted modulated signal, said antenna switch being settable to pass only a selected one of said inputs to said output;

an attenuator connected to receive a signal output by said antenna switch, said attenuator outputting an attenuated version of said signal in accordance with a settable attenuation level;

a converter for converting each modulated signal output by said attenuator to baseband signal components; and

a digital signal processor programmed to perform the following steps;

(a) setting a first attenuation level during receipt of data packets and setting a second attenuation level greater than said first attenuation level during receipt of blank packets during each cycle;

(b) setting said antenna switch to pass a respective blank packet from each of said plurality of receive antennas in a first cycle;

(c) estimating the relative signal power at each of said plurality of receive antennas from said respective blank packets in said first cycle;

(d) setting said antenna switch to pass data packets in a second cycle from a selected one of said plurality of receive antennas based at least in part on the results of said estimating step; and

(e) demodulating the baseband signal components derived from data packets passed by said antenna switch during said second cycle.

5. The communications system as recited in claim 4, further comprising a patient monitor which sends patient monitoring data to said transmitter, said data packets containing patient monitoring data and said blank packets not containing patient monitoring data.

6. The communications system as recited in claim 4, wherein said step of estimating comprises computing a respective relative signal power value for each receive antenna which is a function of the estimated relative signal power for the respective receive antenna.

7. The communications system as recited in claim 6, wherein said function is a weighted average of estimated relative signal power computed over a plurality of cycles.

8. The communications system as recited in claim 7, wherein said estimated relative signal power for the current cycle is weighted more heavily than the estimated signal power for any preceding cycle.