Nec Corporation

Toshihito Kanai

Kojiro Hamabe

Yukitsuna Furuya

Makoto Shibutani

Masanori Taketsugu

Junji Namiki

Katsumi Emura

A radio channel control section 370 transmits and receives to and from an adjacent base station uplink/downlink channel communication qualities measured by a communication channel transmit/receive section 330 and a mobile station 410, respectively, compares them with predetermined lower and upper threshold values Tl/Th, requests a pilot channel transmit section 350 to decrease and increase the transmission power level of a pilot signal if the threshold value Tl is not reached and the threshold value Th is exceeded, respectively. For a downlink channel, a hand-off parameter is increased and decreased if the threshold value Tl is not reached and the threshold value Th is exceeded, respectively. For an uplink channel, the hand-off parameter is decreased and increased if the threshold value Tl is not reached and the threshold value Th is exceeded, respectively.

Radio channel control apparatus used in a CDMA cellular system and

A cellular type mobile communication system has a service area divided into a plurality of cells and comprises in each of the cells a base station for selecting a selected one of first through N-th radio channels as a radio communication channel to carry out bidirectional communication between the base station and a mobile station, where N represents a positive integer which is greater than one. The base station comprises a management memory for memorizing first through N-th traffic amounts on the first through the N-th radio channels, respectively. The first through the N-th traffic amounts are monitored by first through N-th monitoring sections, respectively. A CPU selects the radio communication channel from the first through the N-th radio channels in accordance with the first through the N-th traffic amounts.

Mobile communication system capable of effectively using a radio

A mobile communication system includes an antenna, a first radio transmission/reception unit, a propagation loss calculating section, an antenna gain calculating section, an antenna gain selecting section, and a first weight control circuit. The antenna has a variable directivity pattern. The first radio transmission/reception unit transmits/receives communication information to/from a distant station through a communication channel by using the antenna. The propagation loss calculating section calculates a propagation loss in a radio channel including a communication channel between the antenna and the distant station. The antenna gain calculating section calculates a minimum antenna gain value required for communication under the condition of the propagation loss calculated by the propagation loss calculating section. The antenna gain selecting section selects an antenna gain not less than the minimum antenna gain value calculated by the antenna gain calculating section. The first weight control circuit controls the directivity pattern of the antenna in a communication state on the basis of the antenna gain selected by the antenna gain selecting section.

Mobile communication system which performs antenna gain control

A control method of the direction of directivity of a base station antenna in a mobile communication system which uses a variable directivity antenna at the base station. The direction of directivity is controlled to continuously change such that signal reception level at each mobile station exceeds a prescribed value during the time interval from the beginning of the first slot to the end of the (n+1)th slot of any continuous n+1 (n being a natural number) slots on at least one time-division-multiplexed channel.

Antenna directivity control method and channel configuration method for

The invention provides channel allocation method which achieves a high frequency utilization efficiency while suppressing the average transmission power by transmission power control. Selection priority degrees and initial minimum transmission power control amounts are set for all radio channels allocated to the system. The initial minimum transmission power control amounts are set such that the radio channel having higher selection priority degree has higher or at least equal initial minimum transmission power control amount than the lower selection priority radio channel. Upon channel allocation, a radio channel is selected in accordance with the selection priority degree, by the way that calculating the transmission power control amount of the radio channel (S505 to S507), comparing the transmission power control amount with the initial minimum transmission power control amount (S508), and when the transmission power control amount is equal to or higher than the initial minimum transmission power control amount, then use of the radio channel is permitted.

Method of channel allocation in a mobile telephone system

In a cellular mobile telecommunications system, a radio link control method provides each base station with an antenna whose directivity is adaptively controllable on a mobile station basis. The base station communicates with a plurality of mobile stations by using the same frequency at the same time. The base station selects, among transmitters/receivers thereof which are in communication, two transmitters/receivers using the same frequency, detects the main beam directions of antenna directivities thereof, and then compares a difference between the main beam directions and a predetermined threshold. If the former is smaller than the latter, the base station executes handover so as to replace the frequency being used by one of the transmitters/receivers with another frequency. The method allows a single base station to use the same frequency twice or more while preventing interference from occurring within the base station.

Radio link control method for a mobile telecommunications system

In a channel assignment method for a mobile communication system, each of base stations respectively arranged in a plurality of cells constituting a service area selects one of all speech communication channels in an order of priority common to all the cells in response to a speech communication request from a mobile station. The base station then checks whether the carrier to interference ratio of the selected speech communication channel is equal to or higher than a predetermined level. The selected channel is assigned as a speech communication channel for the cell when it is determined on the basis of the check result that the carrier to interference ratio is equal to or higher than the predetermined level.

Channel assignment method in mobile communication system in which

A cellular mobile communication system in which each of one or more cells is provided with a base radio station, and mobile terminals communicate with the base radio stations. Base radio stations (21, 22 and 23) are connected to a central base station (100) by optical fibers. The central base station is connected to a mobile switching center (50). Each of the base radio stations is provided with an O/E converter (201) and E/O converter (207). The O/E converter converts a optical signal containing speech signals and a call connection control signal into RF signals. The E/O converter (207) converts RF signals, received from a mobile terminal (11) via an antenna (204), into optical signals and transmits the optical signals to the central base station. The central base station comprises O/E converters (301-303) for converting optical signals from each base radio station into RF signals; receivers (401-403) for demodulating these RF signals; transmitters (406-408) for converting speech signals and a call connection control signal from the mobile switching center into RF signals; and E/O converters (304-306) for converting these RF signals into optical signals and transmitting the optical signals to a base radio station.

Mobile communication system

In order to provide for a mobile communication network of a cellular type a transmission power control system capable of keeping a signal quality constant, an average bit error rate y is measured on a receiving side in connection with a communication channel being in use (step 100). If the average bit error rate y is not greater than a first rate threshold value LV1, transmission power is decreased by a predetermined amount on a transmitting side (step 102). If the average bit error rate y is not less than a second rate threshold value LV2 which is greater than the first rate threshold value LV1 (step 103), the transmission power is increased by the predetermined amount on the transmitting side (step 104). Preferably, an average reception level is additionally measured to adjust the transmission power when the bit error rate is less or greater than the first or the second rate threshold value. The first and/or the second rate threshold value is adaptively adjusted by counting the number of times by which the bit error rate exceeds a predetermined maximum allowable rate. It is possible to use an average carrier to interference ratio with threshold ratio values substituted for the threshold rate values and with a predetermined minimum allowable ratio used.

Transmission power control system capable of keeping signal quality

In a cellular mobile communication system, each base station is allocated common frequencies shared with other base stations in addition to unique frequencies. One of the unique frequencies is assigned by a base station to a mobile terminal in response to a call request. The field strength of a signal from that mobile terminal is detected and one of the common frequencies is assigned to it if the detected field strength becomes lower than a threshold. The base station receives a field strength signal from a neighboring station indicating the field strength of a version of the signal at the neighboring station and compares it with a threshold, and combines the signal of that mobile terminal with the version of the signal received by and relayed from the neighboring station when the field strength of that version of the signal is higher than the threshold. At the given mobile station, a signal from the base station which assigned the common frequency is combined with a signal from the neighboring station. In a modification, the field strength of signals from surrounding base stations is detected by mobile terminals and a start-of-diversity-mode request is transmitted when the field strength of one of the surrounding stations is higher than a threshold and an end-of-diversity-mode request signal is transmitted when the field strength of such a surrounding station is lower than the threshold. The base station responds to these requests for effecting diversity reception.

Cellular mobile communications system using frequencies commonly shared

In an antenna arrangement system having a plurality of radio base stations each of which defines a cell approximated by a regular hexagon and divided into six sectors first and second ones of which are directed towards an angle of 0 degree with respect to an x-axis and towards an angle of 180 degrees, respectively, in an orthogonal coordinate system, first and second base stations are selected from the radio base stations to assign a common frequency channel to the first and the second sectors, respectively, and are located at first and second coordinate positions, respectively. The first and the second coordinate positions may be represented by (.sqroot.3 Rni, 3Rj/2) and (.sqroot.3 R(2ni-1)/2, 3Rj/2) where j takes an even number and an odd number, respectively, and R is representative of a real number, n, a natural number; i and j, integers. Alternatively, the first and the second coordinate positions may be represented by (.sqroot.3 Rni, 3Rj/2) and (.sqroot.3 R(3ni-3)/2, 3Rj/2) under the same conditions. The first and the second coordinate positions may not be restricted to the above-exemplified positions.

Antenna arrangement system capable of reducing co-channel interference

When communication is established using a mobile radio terminal, the speed at which the terminal is moving is measured by monitoring the Rayleigh fading of the signal strength. Using this velocity indicative parameter, a threshold level which is used to determine if a handoff is required or not, can be adjusted in a manner which renders the decision process more accurate and minimizes the number of unwarranted handoffs.

Method of controlling handoff in cellular mobile radio communications

According to a handoff method for a cellular digital mobile communication system, a communication test of a new channel is performed by utilizing a free time of a time-divisionally multiplexed channel. A mobile station of this invention includes a communication circuit for performing communication by using a time-divisionally multiplexed channel, a switching circuit for connecting a new channel during a free time of the time-divisionally multiplexed channel, and a communication test circuit for performing a communication test when the switching circuit is connected to the new channel.

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Tokyo, Japan

Toshihito Kanai