CN101521651B - Multiple Access Signal Processing Method for Broadband Satellite Communication Link in Next Generation Communication System - Google Patents

Abstract

A multi-access signal processing method for broadband satellite communication links in the next-generation communication system, which relates to the technical fields of satellite communication and mobile communication, and solves the on-board processing method for the future broadband multimedia satellite system that currently does not have an optimal multiple-access system The problem. In the present invention, there are two kinds of broadband satellite communication link multiple access signal processing methods in the communication system of the next generation: a kind of is to adopt OFDMA mode, and one of its characteristics is to realize high-speed transmission processing simply by fast Fourier transform; Another characteristic is exactly by The cyclic prefix is used to make it more robust to multipath channel loss and intersymbol interference; while at the receiving end, it is a structure with channel estimation and equalization functions. The other adopts the SC-FDMA method, which adds a discrete Fourier transform expansion module after the serial/parallel module, and then enters the fast Fourier inverse transform module, so that the PAPR value decreases. The invention has the advantages of simple realization method, reasonable design, reliable performance and great popularization value.

Description

Multiple Access Signal Processing Method for Broadband Satellite Communication Link in Next Generation Communication System

technical field

The invention relates to the technical field of satellite communication and mobile communication, in particular to a method for processing multiple access signals of a broadband satellite communication link in a next-generation communication system.

Background technique

The satellite communication system is the most basic part of the next-generation communication system. The use of satellites for communication can better meet the needs of high-speed, high-quality and multimedia services in the next-generation communication. The space segment and the ground segment of the satellite are used to form an integrated multi-layer communication architecture.

Although current satellite systems can provide higher bit rates and higher capacity than conventional systems by using different frequency bands, their bit rates are still much lower than 3G or 4G terrestrial mobile systems. In order to meet the business needs of this new integrated system of the space segment and the ground segment, more challenges are brought to the air interface technology. Due to the differences between satellite systems and terrestrial wireless systems, there is no ultimate optimal multiple address system for future satellite systems. Although there are many multiple access technologies, such as CDMA, TDMA, and FDMA, each is only suitable for different application forms. Although these methods can provide more optimized solutions for fixed services, they cannot also show better characteristics in the next generation of broadband communication services. The goal of the future B3G or 4G broadband communication system is the seamless roaming of the space segment and the ground segment. Therefore, how to select a multiple access method suitable for satellite links is a necessary problem to be solved in the next generation wireless communication system.

The next generation wireless communication system is an integrated system consisting of a satellite-based space segment and a ground segment. Although a variety of multiple access systems have been proposed, the broadband satellite communication link, especially the access method of the downlink is not very clear yet. OFDMA based on OFDM technology and SC-FDMA system based on DFT-S-OFDM have become optional access methods for satellite links because of their own advantages. However, the problem is that OFDM has a high peak-to-average power ratio (PAPR) characteristic, which will cause losses in the high power amplifier (HPA).

Contents of the invention

In order to solve the problem that the future broadband multimedia satellite system does not have an optimal multiple access system on-board processing method, the present invention proposes a broadband satellite communication link multiple access signal processing method in the next generation communication system.

There are two kinds of broadband satellite communication link multiple access signal processing methods in the next generation communication system in the present invention: a kind of is the broadband satellite communication link multiple access signal processing method in the next generation communication system of OFDMA mode, another kind adopts SC - A method for processing a broadband satellite communication link multiple access signal in a next generation communication system in the FDMA mode.

The transmission signal processing method using OFDMA mode in the uplink:

Step A1, the input bit stream is encoded and then serial/parallel converted to obtain a parallel frequency domain signal sequence, and then the constellation point symbols are obtained through mapping, and the constellation point symbols are modulated to obtain a parallel symbol stream X'(n);

Step A2, the parallel frequency domain signal sequence X'(n) and the parallel frequency domain pilot signal sequence P'(n) are subjected to frequency domain pilot insertion, and then the parallel time domain is obtained by inverse fast Fourier transform (IFFT) Signal sequence X(n) and time domain pilot signal sequence P(n);

Step A3, after inserting the cyclic prefix into the parallel time-domain signal sequence X(n), a parallel time-domain signal sequence Z(n) is obtained;

Step A4, the parallel time-domain signal sequence Z(n) is converted to parallel/serial, and then sent to the ground receiver through the satellite-ground channel;

The downlink uses the OFDMA method to process the received signal:

Step A5, the received time-domain reception signal sequence C(n) is divided into two paths for transmission: performing serial/parallel conversion to obtain parallel time-domain reception signal sequence and time-domain pilot signal sequence P(n);

Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix all the way to obtain parallel frequency domain signal sequence D'(n);

Another way to perform channel estimation to obtain a parallel channel frequency response sequence

进行迫零均衡后得到并行的估计信号序列

Step A7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence

After zero-forcing equalization, a parallel estimated signal sequence is obtained

进行并/串转换、解映射和解调后输出信号。Step A8, parallel estimated signal sequence

Perform parallel/serial conversion, demapping and demodulation to output signals.

The transmission signal processing method using SC-FDMA mode in the uplink:

Step B1, the input bit stream is encoded and mapped to obtain constellation point symbols, the constellation point symbols are modulated to obtain a symbol stream, and then serial/parallel converted to obtain a parallel frequency domain signal sequence X"(n);

Step B2, after the parallel frequency-domain signal sequence X″(n) and the parallel time-domain pilot signal sequence P′(n) are inserted into the frequency-domain pilot, X′(n) is obtained through the discrete Fourier transform (DFT) expansion module ), after the Inverse Fast Fourier Transform (IFFT) transformation, the parallel time-domain signal sequence X(n) and time-domain pilot signal sequence P(n) are obtained;

Step B3, after the parallel time-domain signal sequence X(n) is inserted into the cyclic prefix, parallel/serial conversion is performed to obtain the parallel time-domain signal sequence Z(n);

Step B4, the parallel time-domain signal sequence Z(n) is then sent to the ground receiver through the satellite-ground channel;

The received signal processing method using SC-FDMA mode in the downlink:

Step B5, performing serial/parallel conversion on the received signal to obtain parallel time-domain received signal sequence C(n) and time-domain pilot signal sequence P(n);

Step B6, the parallel time-domain received signal sequence C(n) is divided into two paths for transmission:

Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix all the way to obtain parallel frequency domain signal sequence D'(n);

The other channel estimates the channel to obtain the channel impulse response Then perform fast Fourier transform (FFT) transformation to obtain parallel channel frequency response sequence

Step B7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence After zero-forcing equalization, a parallel estimated signal sequence is obtained

进行并/串转换、解映射和解调后输出信号。Step B8, parallel estimated signal sequence

Perform parallel/serial conversion, demapping and demodulation to output signals.

The invention utilizes the new technology and new system of the existing mobile communication, can better promote the integration of the next generation satellite communication system and the existing ground wireless system, and improve the performance of the satellite communication system.

OFDM is a high-efficiency transmission system in wireless channels. Its most important feature is that it has strong anti-multipath and narrow-band interference capabilities in frequency-selective channels, mainly due to the use of cyclic prefixes in applications. The effect of (CP) as a guard interval. It is very necessary for the receiver to use pilot-aided channel estimation in the application, and its combination with equalization can improve the performance of the receiving end very well. The traditional time-domain equalization is more complex than the frequency-domain equalization. Therefore, frequency domain equalization is generally adopted at the receiver side. In addition, OFDM technology just meets the demand for high spectral efficiency. Moreover, it can achieve higher frequency efficiency by reducing the number of subcarriers and guard bands, and it is more flexible for different users. In addition, the OFDM technology based on DFT can reduce the equipment complexity of the base station. Therefore, the technology based on OFDM system is a better solution for satellite links.

OFDMA can be regarded as a multi-user version of the OFDM system, or as an OFDM form with TDMA. The multiple access of OFDMA is realized by assigning subcarrier groups to each user. Thus, low-speed data transmission with constant delay and shorter delays from different users are allowed in this system. However, OFDMA can also be viewed as a joint form of frequency-domain and time-domain multiple access, where resources are allocated in time-frequency space and OFDM symbols are slotted as sequences of OFDM subcarriers. Therefore, OFDMA is considered to be the most suitable multiple access method for broadband wireless networks because of its friendliness such as MIMO and the advantages of frequency selectivity that can fully utilize channels. However, OFDM has been questioned due to its high PAPR characteristic leading to high power amplifier (HPA) losses.

SC-FDMA based on DFT-S (Spreading)-OFDM is another alternative form of OFDMA, and it can also be regarded as an interleaved FDMA. In fact, the principle of DFT-S (Spreading)-OFDM is the same as OFDM. At present, SC-FDMA has been adopted by the uplink of 3GPP LTE because of its lower PAPR compared with OFDMA, and OFDMA can obtain more advanced features through flexible frequency interval settings.

The realization method of the present invention is simple, and under the background of the proposed next-generation broadband satellite communication system, it can be effectively realized by changing the corresponding design of the on-board processing module according to different access schemes; at the same time, the present invention has reasonable design and reliable performance , has great promotional value.

Description of drawings

Fig. 1 is the structural representation of next generation communication system of the present invention; Fig. 2 is the flow chart of broadband satellite communication link multiple access signal processing method in the next generation communication system adopting OFDMA mode; Fig. 3 is the next generation adopting SC-FDMA mode A flow chart of a method for processing a broadband satellite communication link multiple access signal in a communication system; FIG. 4 is a schematic structural diagram of an on-board processing module of the present invention.

Detailed ways

Specific embodiment one: illustrate this embodiment in conjunction with Fig. 1 to Fig. 4; The next generation communication system in this embodiment is made up of space segment and ground segment; Space segment is by a GEO satellite and has inter-satellite link (ISL) Composed of LEO satellites; while multimedia services and data are transmitted through up/down links; the ground segment is based on different networks, especially all-IP networks.

Based on OFDM technology, there are two methods for processing broadband satellite communication link multiple access signals in the next generation communication system: one is the method of processing broadband satellite communication link multiple access signal in the next generation communication system using OFDMA, and the other is using SC - A method for processing a broadband satellite communication link multiple access signal in a next generation communication system in the FDMA mode.

The transmission signal processing method using OFDMA mode in the uplink:

Step A1, the input bit stream is encoded and then serial/parallel converted to obtain a parallel frequency domain signal sequence, and then the constellation point symbols are obtained through mapping, and the constellation point symbols are modulated to obtain a parallel symbol stream X'(n);

Step A2, the parallel frequency domain signal sequence X'(n) and the parallel frequency domain pilot signal sequence P'(n) are subjected to frequency domain pilot insertion, and then the parallel time domain is obtained by inverse fast Fourier transform (IFFT) Signal sequence X(n) and time domain pilot signal sequence P(n);

Step A3, after inserting the cyclic prefix into the parallel time-domain signal sequence X(n), a parallel time-domain signal sequence Z(n) is obtained;

Step A4, the parallel time-domain signal sequence Z(n) is converted to parallel/serial, and then sent to the ground receiver through the satellite-ground channel;

The downlink uses the OFDMA method to process the received signal:

Step A5, the received time-domain reception signal sequence C(n) is divided into two paths for transmission: performing serial/parallel conversion to obtain parallel time-domain reception signal sequence and time-domain pilot signal sequence P(n);

Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix along the way to obtain a parallel frequency domain signal sequence D'(n);

Another way to perform channel estimation to obtain a parallel channel frequency response sequence

进行迫零均衡后得到并行的估计信号序列 Step A7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence

After zero-forcing equalization, a parallel estimated signal sequence is obtained

Step A8, parallel estimated signal sequence Perform parallel/serial conversion, demapping and demodulation to output signals.

The first characteristic of using the OFDMA access system in both the uplink and downlink of this method is that it can simply realize high-speed transmission processing through fast Fourier transform (FFT). Multiple data is transmitted over multiple subcarriers, so the data rate is reduced. At the same time, wideband channels are divided into narrowband channels, which can resist inter-symbol interference. Another feature is that it is robust to multipath channel loss and intersymbol interference (ISI) by using a cyclic prefix (CP). The CP is the repetition of the last part of the original OFDM symbol added in front of each symbol, and in order to avoid ISI and inter-subcarrier interference (ICI), the duration of the CP is generally longer than the maximum time of the channel. On the premise of considering accurate synchronization, the present invention considers a structure with channel estimation and equalization functions at the receiving end.

The transmission signal processing method using SC-FDMA mode in the uplink:

Step B1, the input bit stream is encoded and mapped to obtain constellation point symbols, the constellation point symbols are modulated to obtain a symbol stream, and then serial/parallel converted to obtain a parallel frequency domain signal sequence X"(n);

Step B2, after the parallel frequency-domain signal sequence X″(n) and the parallel time-domain pilot signal sequence P′(n) are inserted into the frequency-domain pilot, X′(n) is obtained through the discrete Fourier transform (DFT) expansion module ), after the Inverse Fast Fourier Transform (IFFT) transformation, the parallel time-domain signal sequence X(n) and time-domain pilot signal sequence P(n) are obtained;

Step B3, after the parallel time-domain signal sequence X(n) is inserted into the cyclic prefix, parallel/serial conversion is performed to obtain the parallel time-domain signal sequence Z(n);

Step B4, the parallel time-domain signal sequence Z(n) is then sent to the ground receiver through the satellite-ground channel;

The received signal processing method using SC-FDMA mode in the downlink:

Step B5, performing serial/parallel conversion on the received signal to obtain parallel time-domain received signal sequence C(n) and time-domain pilot signal sequence P(n);

Step B6, the parallel time-domain received signal sequence C(n) is divided into two paths for transmission:

Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix all the way to obtain parallel frequency domain signal sequence D'(n);

而后进行快速傅立叶变换(FFT)变换后得到并行的信道频率响应序列

The other channel estimates the channel to obtain the channel impulse response

Then perform fast Fourier transform (FFT) transformation to obtain parallel channel frequency response sequence

进行迫零均衡后得到并行的估计信号序列

Step B7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence

After zero-forcing equalization, a parallel estimated signal sequence is obtained

进行并/串转换、解映射和解调后输出信号。Step B8, parallel estimated signal sequence

Perform parallel/serial conversion, demapping and demodulation to output signals.

SC-FDMA can also be called DFT-OFDM. Its biggest feature is that under the same circumstances, compared with OFDM, SC-FDMA has better PAPR performance. It has a lower PAPR value than OFDM. Although the SC-FDMA system has a similar principle to OFDMA, it adds a discrete Fourier transform (DFT) expansion module after the serial/parallel module, and then enters the inverse fast Fourier transform (IFFT) module, which reduces the PAPR value.

OFDM and DFT-S-OFDM modules are used on the on-board processing module.

On-board switching is used to distribute TDM data from a given gateway to each beam according to different routes. And adopting simple Fast Fourier Transform (FFT) The device can simplify the structure of on-star switching, because there is no need for complicated carrier demultiplexing filters to separate the carriers.

First, the signal is processed by a low-noise amplifier (LNA) and an inversion multiplexer (IMUX), and then according to the requirements of the OFDMA or SC-FDMA system, the corresponding OFDM or DFT-S-OFDM modulation module is used on the star The module demodulates the signal output from the inverse multiplexer (IMUX) accordingly, and then modulates it after on-board switching based on IP/MPLS switching technology;

Then, the signal passing through the high power amplifier (HPA) module and the output multiplexer (OMUX) filter bank is transmitted to the link channel through the antenna;

When there is a line-of-sight path LOS, the channel of the link is a model of frequency-selective Rice fading, and when the line-of-sight path LOS does not exist, the envelope of the channel response of the link will obey the Rayleigh distribution.

Claims (2)

1. The multi-access signal processing method of broadband satellite communication link in the next generation communication system, characterized in that The next-generation communication system consists of a space segment and a ground segment; the space segment consists of a GEO satellite and a LEO satellite with an inter-satellite link; the on-board processing module uses OFDM and DFT-S-OFDM modules; The transmission signal processing method using OFDMA mode in the uplink: Step A1, the input bit stream is encoded and then serial/parallel converted to obtain a parallel frequency domain signal sequence, and then the constellation point symbols are obtained through mapping, and the constellation point symbols are modulated to obtain a parallel symbol stream X'(n); Step A2, the parallel frequency domain signal sequence X'(n) and the parallel frequency domain pilot signal sequence P'(n) are subjected to frequency domain pilot insertion, and then the parallel time domain is obtained by inverse fast Fourier transform (IFFT) Signal sequence X(n) and time domain pilot signal sequence P(n); Step A3, after inserting the cyclic prefix into the parallel time-domain signal sequence X(n), a parallel time-domain signal sequence Z(n) is obtained; Step A4, the parallel time-domain signal sequence Z(n) is converted to parallel/serial, and then sent to the ground receiver through the satellite-ground channel; The downlink uses the OFDMA method to process the received signal: Step A5, the received time-domain reception signal sequence C(n) is divided into two paths for transmission: performing serial/parallel conversion to obtain parallel time-domain reception signal sequence and time-domain pilot signal sequence P(n); Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix all the way to obtain parallel frequency domain signal sequence D'(n); Another way to perform channel estimation to obtain a parallel channel frequency response sequence

Step A7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence

After zero-forcing equalization, a parallel estimated signal sequence is obtained

Step A8, parallel estimated signal sequence Perform parallel/serial conversion, demapping and demodulation to output signals. 2. The multi-access signal processing method of broadband satellite communication link in the next generation communication system, characterized in that The next-generation communication system consists of a space segment and a ground segment; the space segment consists of a GEO satellite and a LEO satellite with an inter-satellite link; the on-board processing module uses OFDM and DFT-S-OFDM modules; The transmission signal processing method using SC-FDMA mode in the uplink: Step B1, the input bit stream is encoded and mapped to obtain constellation point symbols, the constellation point symbols are modulated to obtain a symbol stream, and then serial/parallel converted to obtain a parallel frequency domain signal sequence X"(n); Step B2, after the parallel frequency-domain signal sequence X″(n) and the parallel time-domain pilot signal sequence P′(n) are inserted into the frequency-domain pilot, X′(n) is obtained through the discrete Fourier transform (DFT) expansion module ), after the Inverse Fast Fourier Transform (IFFT) transformation, the parallel time-domain signal sequence X(n) and time-domain pilot signal sequence P(n) are obtained; Step B3, after the parallel time-domain signal sequence X(n) is inserted into the cyclic prefix, parallel/serial conversion is performed to obtain the parallel time-domain signal sequence Z(n); Step B4, the parallel time-domain signal sequence Z(n) is then sent to the ground receiver through the satellite-ground channel; The received signal processing method using SC-FDMA mode in the downlink: Step B5, performing serial/parallel conversion on the received signal to obtain parallel time-domain received signal sequence C(n) and time-domain pilot signal sequence P(n); Step B6, the parallel time-domain received signal sequence C(n) is divided into two paths for transmission: Perform fast Fourier transform (FFT) transformation after removing the cyclic prefix all the way to obtain parallel frequency domain signal sequence D'(n); The other channel estimates the channel to obtain the channel impulse response

Then perform fast Fourier transform (FFT) transformation to obtain parallel channel frequency response sequence

Step B7, parallel frequency domain signal sequence D'(n) and parallel channel frequency response sequence After zero-forcing equalization, a parallel estimated signal sequence is obtained

Step B8, parallel estimated signal sequence Perform parallel/serial conversion, demapping and demodulation to output signals.

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