Abstract:
The present invention relates to methods for power control and link adaptation techniques to compensate for a long round trip delay time and slow channel fading in an lte-based mobile communication system system having a long round trip delay time, such as a satellite mobile. The methods are capable of: compensating for a long round trip delay time in a satellite mobile system having a longer distance between a base station and a terminal compared to a terrestrial lte system; supporting a MCS level requested by a terminal by predicting a channel in a round trip delay time, maintaining compatibility within an existing lte frame by generating a TPC instruction per frame to control uplink closed loop power; and compensating for slow channel fading in a satellite mobile system having a longer distance between a base station and a terminal compared to a territorial lte system. [Reference numerals] (AA) Start;(BB) Measure the strength of a signal receiving a frame unit upward link;(CC) Determine TPC where a channel expectation value is reflected;(DD) Transmit TPC from a base station to a terminal;(EE) Determine a delay compensation power control value by using the received current TPC and the past TPC;(FF) Reflect the delay compensation power control value to a terminal transmitting power;(GG) Transmit data from the terminal to the base station;(HH) End
Abstract:
PURPOSE: A communication method in a mobile communication system which has a multi-cell and a beam forming apparatus thereof are provided to efficiently have frequency reusability 1. CONSTITUTION: A beam formation controlling unit (16) sets up a beam section which forms a beam of the smallest size and a beam sector which includes multiple beam sections based on obtained information about mobile terminals. A beam forming unit for each group (13) forms one beam for each beam group which includes multiple beam sectors. A beam forming unit for each sector (14) forms one beam for each beam sector. A beam forming unit for each section (15) forms one beam for each beam section. [Reference numerals] (11) Terminal location information acquisition unit; (12) Parameter information acquisition unit; (13) Beam forming unit for each group; (14) Beam forming unit for each sector; (15) Beam forming unit for each section; (16) Beam formation controlling unit; (161) Beam electricity setting unit
Abstract:
PURPOSE: A random access method is provided to detect a random access preamble by acquiring a correlation for one root value from a base station. CONSTITUTION: A base station transmits system information including a root value respectively selected from a root set to a terminal(S20). The terminal transmits a random access preamble to the base station(S30). The base station establishes a feasible arrival section of the random access preamble(S40). The base station detects the random access preamble within the feasible arrival section(S50).
Abstract:
A communication method in a mobile communication system is provided to supply a multimedia broadcasting service by using a layered modulation method in a satellite mobile communication system having a complementary terrestrial component. A satellite produces a signal transmitted to a complementary terrestrial component and a terminal(S100). The satellite transmits the produced signal to the complementary terrestrial component and the first terminal(S115). The first terminal modulates the second layer modulation signal among signals received from the satellite to use broadcasting contents included in a corresponding signal(S125). The complementary terrestrial component amplifies the layer modulation signal received from the satellite and transmits the amplified signal to the second terminal(S130).
Abstract:
방송 및 통신 서비스를 동시에 지원하는 위성 이동통신 시스템을 위한 지상 보조 장치의 신호 전송 방법 및 그 지상 보조 장치가 개시된다. 본 발명에 따르면 지상 보조 장치는 공중 전송 장치로부터 양방향 통신 서비스를 위한 데이터인 통신 데이터와 방송 서비스를 위한 데이터인 방송 데이터를 하향링크의 서로 다른 주파수 대역, 즉 서로 다른 반송파를 통해 또는 같은 주파수 대역, 즉 같은 반송파를 통해 동시에 수신하고, 부가적인 데이터를 추가하여 그 방송 데이터와 부가적인 데이터를 서로 다른 주파수 대역을 통해 또는 같은 주파수 대역을 통해 단말들에 전송한다. 이로써 그 지상 보조 장치를 포함한 위성 이동통신 시스템은 양방향 통신 서비스와 방송 서비스를 동시에 효과적으로 지원할 수 있다. 지상 보조 장치, 위성, 이동통신, 방송
Abstract:
An apparatus and a method for receiving a digital signal based on an OFDM are provided to decide a time synchronizing point for minimizing ISI(Inter-Symbol Interference) and to perform the channel estimation accurately, at the same time. An apparatus for receiving a digital signal comprises a signal receiving part(100), a time synchronizing estimating part(101), a channel estimating part(102), and a data restoring part(103). The signal receiving part receives a signal which is modulated by an OFDM using a preamble including a CAZAC(Constant Amplitude Zero Auto Correlation) sequence. The time synchronizing estimating part measures the degree of cross-correlation between the received digital signal and the preamble and a power value of the received digital signal, calculates a point at which the ISI is minimal, and estimates the point as a time synchronizing point. The channel estimating part estimates a channel compensation value through a first fast Fourier transform using the time synchronizing point and the degree of cross-correlation. The data restoring part restores data using the time synchronizing point and the channel compensation value.
Abstract:
A method and an apparatus for handover in a mobile communication network comprising a satellite communication system are provided to enable handover to be efficiently carried out in a shadow area of a terrestrial communication system by reflecting the RSSI(Received Signal Strength Indicator) characteristics of a satellite communication system in order to prevent various problems which can be generated when handover is executed between the satellite communication system and the terrestrial communication system. In a mobile communication network comprising a plurality of base stations and a communication satellite, a mobile terminal calculates the RSSI of the present base station. Then the mobile terminal calculates the RSSIs of other base stations and the RSSI of the communication satellite(603). The mobile terminal selects a base station having the maximum RSSI among the calculated RSSIs, except the RSSI of the present base station(606). In case the RSSI of the present base station is less than the minimum handover power, the difference between the RSSI of the selected base station and the RSSI of the present base station is smaller than the first terrestrial handover sensitivity, and another base station with which the mobile terminal can communicate does not exist, the mobile terminal executes handover to the communication satellite(609-621).
Abstract:
A time synchronization method using a preamble having a good autocorrelation of multiply inter-sequences in an OFDM(Orthogonal Frequency-Division Multiplexing) communication network and a frequency offset estimation method using the same are provided to match a time synchronization and estimates a frequency offset based on the time offset without transmitting a pilot symbol, a cyclic prefix, or a virtual carrier wave. A time synchronization method using a preamble having a good autocorrelation of multiply inter-sequences in an OFDM(Orthogonal Frequency-Division Multiplexing) communication network includes the steps of: if receiving a signal having a preamble from a transmission device, performing a moving sum of the received preamble and a stored CAZAC sequence; estimating a position of a received signal corresponding to a result value of the performing of the moving sum having a maximum value; and matching time synchronization of the received time based on the estimated position.
Abstract:
1. 청구범위에 기재된 발명이 속한 기술분야 본 발명은, 무선통신 단말기에서의 패킷 전송 방법에 관한 것임. 2. 발명이 해결하려고 하는 기술적 과제 본 발명은, 슬롯방식 알로하 임의접속방식과 자동재전송요구 오류정정방식을 이용하는 무선통신 단말기에서 기지국 등으로 패킷 전송시, 채널 환경에 따라 패킷의 전송 간격을 조절함으로써, 타 무선통신 단말기로부터 전송되는 패킷과의 충돌 확률을 감소시켜 패킷의 전송 효율을 증가시키기 위한, 무선통신 단말기에서의 패킷 전송 방법을 제공하는데 그 목적이 있음. 3. 발명의 해결방법의 요지 본 발명은, 슬롯방식 알로하 임의접속방식(Slotted Aloha Random Access Control)과 자동재전송요구 오류정정방식을 결합하여 상향링크 패킷을 전송하는 긴 왕복지연시간을 가지는 무선통신 단말기에서의 패킷 전송 방법에 있어서, 임의의 크기를 가지는 자동재전송요구(ARQ) 버퍼에 상향링크 전송 패킷을 저장하는 패킷 저장단계; 상기 자동재전송요구(ARQ) 버퍼에 저장되어 있는 패킷을 제 1 슬롯 간격으로 전송하는 제 1 패킷 전송단계; 상기 전송한 패킷에 대한 비정상 피드백 정보를 연속하여 소정 회수 수신함에 따라 평균 왕복지연시간과 상기 자동재전송요구 버퍼의 크기를 이용하여 제 2 슬롯 간격을 산출하는 단계; 상기 산출한 제 2 슬롯 간격으로 추가 상향링크 전송 패킷을 전송하는 제 2 패킷 전송단계; 및 상기 제 2 슬롯 간격으로 전송한 패킷에 대한 정상 피드백 정보를 소정 회수 연속하여 수신함에 따라 상기 제 1 슬롯 간격으로 변경하는 슬롯 간격 변경단계를 포함함. 4. 발명의 중요한 용도 본 발명은 통신 시스템 등에 이용됨. 패킷 전송, 슬롯 간격 조절, 임의접속방식, 자동재전송요구 방식, 자동재전송요구 버퍼, 패킷 충돌 방지