JPH11355827A - Multiple frequency band mobile communication station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power of a mobile station required for retrieving the coverage area of a ground base station or an orbit satellite station. SOLUTION: A CPU 13 gives a command to a DSP 12 for retrieving three frequencies at maximum in a TDMA frame when retrieving. The CPU 13 sequentially gives the three frequencies to be checked to the DSP 12 to retrieve all ground frequency bands. This cycle continues under the condition that there is a detection signal with power enough to be strong to set up an AGC in an RF stage 10 until an RSSI level is received. The CPU 13 arranges the frequencies in the order of higher RSSI levels. When the level is higher than a threshold level, the CPU 13 gives a command to the DSP 12 to be synchronous with the channel. The DSP 12 tries to decode a broadcast message by synchronizing its operation with respect to accurate transmission timing, and a frequency at first and then tries to decode a synchronization burst. When the trial is successful, the CPU 13 registers it, the mobile station completes the operation at the outside of its coverage and 'stays' in the found-out channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-frequency band mobile communication station used in a multi-network environment, for example, in an environment where a network of ground base stations and another network of orbiting satellite stations are present.

[0002]

BACKGROUND OF THE INVENTION Mobile stations need to be able to be established when they are in the coverage area of a terrestrial base station or an orbiting satellite station, but the operation required to enable the mobile station to search for such stations is to use power. Consume.

[0003]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a mobile station which overcomes this problem.

[0004]

SUMMARY OF THE INVENTION A mobile communication station according to the present invention comprises a radio receiver operable in a plurality of different frequency bands used by various networks, and a priority for each network of the networks where at least one network is preferred. Network priority data storage means for storing data identifying the level of the network, and search control means for determining a search frequency for searching each network according to the priority data.

[0005] The search control means preferably changes the search strategy according to the network stations identified in the previous search.
For example, for a GSM / satellite dual mode mobile station, the search control means typically reduces the frequency of satellite searches to a minimum. If the mobile station is not within the coverage area of either the GSM base station or the satellite base station, both satellite search and GSM search will be more frequent. If the mobile station is not in the coverage area of the GSM base station, but is still in the coverage area of the satellite network, the frequency of GSM searches will not decrease.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a multi-frequency band multiplex mode mobile communication station, and FIG. 2 is a flowchart of software used in the mobile station to control a search operation.

FIG. 1 shows a basic block diagram of a mobile telephone. That is, the RF stage 10 for reception and transmission
And frequency shifting components and filtering, calibration, DA
C, an interface stage 11 having an ADC function;
There are a DSP 12 for executing an algorithm for voice encoding / decoding and control / synchronization of various frequencies, and a CPU 13 for controlling telephone functions according to data stored in a ROM 14 and a SIM module (personal ID card) 15.

In particular, the CPU 13 is in charge of a search timing for the nearest ground base station and satellite station. During the search operation, the CPU 13 issues a command to the DSP 12 to search for a maximum of three frequency values in one TDMA frame. The CPU 13 supplies the three frequency values to be checked to the DSP 12, and sequentially searches the entire terrestrial frequency band. This cycle typically continues until there is a strong detection signal such that AGC is established in the RF stage 10 and the next RSSI level is received. The CPU 13 arranges the frequencies in descending order of the RSSI level. If any of them is higher than the threshold, the CPU instructs the 13 DSP 12 to synchronize with the channel. DSP 12 first attempts to decode the broadcast message by synchronizing its operation to the correct timing and frequency of the transmission, and then attempts to decode the synchronization burst. If successful, it is registered by the CPU 13 and the mobile station ends the out-of-area (OOZ) operation and "stays" on the found channel.

[0009] Operation in the terrestrial and satellite frequency bands involves different RF tuning procedures and different protocols for channel recognition and signal decoding. Therefore,
When searching for a terrestrial channel, DSP 12, interface 11, and RF stage 10 must operate in one mode, and when searching for a satellite channel, must operate in another mode. FIG. 1 shows a CP for switching blocks between modes as needed.
A mode control switch 10a controlled by U13,
Each block 10, 11 and 12 having 11a and 12a is shown.

The CPU 13 is programmed to give priority to ground operations. The network priority data is stored in the CPU ROM 13 (preferably in the EROM) as a network list at consecutive addresses in the memory.
(EPROM) or SIM 15. The list includes GSM 900MHz, GSM 1800M
It is assumed that the names of the networks are included, such as Hz, satellite or network name token, and that the networks are listed in order of priority. In the embodiment described here, GSM 900 MHz is the highest priority network, and satellite is the lowest priority network. Such prioritization is shown in FIG. As shown, based on a determination as to whether the mobile station is currently in OOZ operation or staying on a satellite or terrestrial channel, CPU 13 instructs DSP 12 to search at various intervals. When the mobile station is in the OOZ operation state, a ground search is performed every 30 seconds, and a satellite search is performed every two minutes. If the mobile station remains on a satellite network channel, the terrestrial frequency band is searched every two minutes. If the mobile station remains on the terrestrial channel, the satellite frequency band is searched every 5 minutes.

It will be apparent to one skilled in the art that the above principles can be extended to mobile stations that can operate in more than two frequency bands and in more than two different modes.

[Brief description of the drawings]

FIG. 1 is a block diagram of a multi-frequency band multiplex mode mobile communication station.

FIG. 2 is a flowchart of software used in a mobile station to control a search operation.

[Explanation of symbols]

 Reference Signs List 10 RF stage 11 Interface 12 DSP 13 CPU 14 ROM 15 SIM module 10a, 11a, 12a Mode control switch

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Christoph Joan, UK Berkshire ARG 20 TD, Reading, Imperial Way, Imperium, Level 3, NEC Technologies UK Limited Inside

Claims (4)

[Claims] 1. A wireless receiver operable in a plurality of different frequency bands used by various networks, and a network priority storing data identifying a priority level for each of the networks where at least one network is preferred. A mobile communication station having degree data storage means and search control means for determining a search frequency for searching each network according to priority data. 2. The mobile communication station according to claim 1, wherein said search control means operates to change a search frequency of each network according to whether the mobile station is staying on one channel. 3. The mobile communication station according to claim 2, wherein when the mobile station is not staying on a certain channel, the search control means operates to search for a network having a higher priority than other networks. 4. If the mobile station remains on the channel of its higher priority network, the search control means is lower than searching for the higher priority network if it stays on another network. 3. The mobile communication station according to claim 2, which operates to search for another network at a frequency.