CN100365945C - Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code - Google Patents

Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code Download PDF

Info

Publication number
CN100365945C
CN100365945C CNB2005100282367A CN200510028236A CN100365945C CN 100365945 C CN100365945 C CN 100365945C CN B2005100282367 A CNB2005100282367 A CN B2005100282367A CN 200510028236 A CN200510028236 A CN 200510028236A CN 100365945 C CN100365945 C CN 100365945C
Authority
CN
China
Prior art keywords
spread spectrum
unit
code
channel
node
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
CNB2005100282367A
Other languages
Chinese (zh)
Other versions
CN1719741A (en
Inventor
陈西豪
陈惠民
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Shanghai for Science and Technology
Original Assignee
University of Shanghai for Science and Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Shanghai for Science and Technology filed Critical University of Shanghai for Science and Technology
Priority to CNB2005100282367A priority Critical patent/CN100365945C/en
Publication of CN1719741A publication Critical patent/CN1719741A/en
Priority to PCT/CN2006/001898 priority patent/WO2007012289A1/en
Application granted granted Critical
Publication of CN100365945C publication Critical patent/CN100365945C/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
    • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
    • H04B7/2662—Arrangements for Wireless System Synchronisation
    • H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
    • H04B7/2678—Time synchronisation
    • H04B7/2687—Inter base stations synchronisation
    • H04B7/2693—Centralised synchronisation, i.e. using external universal time reference, e.g. by using a global positioning system [GPS] or by distributing time reference over the wireline network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7073—Synchronisation aspects
    • H04B1/7075—Synchronisation aspects with code phase acquisition
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/707—Spread spectrum techniques using direct sequence modulation
    • H04B1/7097—Interference-related aspects
    • H04B1/711—Interference-related aspects the interference being multi-path interference
    • H04B1/7115—Constructive combining of multi-path signals, i.e. RAKE receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/10—Code generation

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The present invention discloses a spread spectrum communication system and an acentric wireless network for realizing code division multiple access by using different phase sequences of a single spread spectrum code. The spread spectrum communication system comprises a satellite receiving clock extraction unit, a clock synchronization unit, a time slot generation control unit, a match unit, a correlation multiple-path selection unit, a demodulation unit, a control processing unit, a PN code unit generator, a code multiple-path selection unit, a spread spectrum modulation unit and a duplexer, wherein a clock receiving unit receives wireless signals and extracts clocks from the wireless signals for the use of the system; the clock synchronization unit generates code piece clock pulses synchronization with data clocks; the match receiving element receives the wireless signals and generates multiple-path match corresponding signals; the correlation multiple-path selection unit selects correlation values in an appointed time slot and outputs the correlation values to the demodulation unit which completes the demodulation of information carried by correlation peaks the control processing unit reads correlation data values in appointed time slots of appointed correlation peaks under the control of control time slots; each correlation data in one period is processed to judge the conditions of the impulse level size of each correlation peaks, etc. according to the service conditions of channels, appropriate phase position sequences are selected as spread spectrum codes for transmission signals, or the two communication parties negotiate to select phase position sequences as local spread spectrum codes for correlation reception. Because the spread spectrum communication system uses different phase sequences of a single spread spectrum code to realize code division, mobile nodes can independently realize the dynamic assignment of the spread spectrum code sequences, and the.

Description

Spread spectrum communication system of code division multiple access and centerless wireless network
Technical Field
The invention relates to a spread spectrum communication system for realizing code division multiple access by adopting a code set formed by different phase sequences of a single spread spectrum code, which can be applied to a wireless network, in particular to a wireless mobile communication network formed by a plurality of centerless mobile nodes.
Background
There are two types of wireless networks that employ spread spectrum techniques: one is a centralized wireless network, such as a CDMA mobile communication system, each mobile station is responsible for dynamic allocation of spreading codes (i.e. channel allocation) by a base station, and even if two mobile stations are in a cell, communication between the two mobile stations must be realized by forwarding through the base station; the other type is a wireless network without a center, such as a wireless Ad Hoc network (wireless Ad Hoc network) and a wireless sensor network, and the nodes of the network can directly realize point-to-point communication without a base station or other management control equipment. And when the direct link connection between two communication nodes cannot be realized due to power or other reasons, other nodes in the network can help forwarding to realize the intercommunication of the nodes in the network. The topology of such networks is dynamically changing, since the nodes are moving at any time. The communication mode between them cannot directly follow the communication mode of the communication network of the existing infrastructure.
Spread spectrum techniques are used in wireless networks and have many advantages, of which it is important to combat fading and implement cdma access with high network throughput. Therefore, at present, in a wireless network without a center, there are many systems that use spread spectrum technology to realize communication. In a direct spread spectrum communication system, a suitable spreading code is at the core of the system, and all key technologies are spread around the spreading code. In a CDMA mobile communication system, a mobile station performs despreading and Multiple Access Interference (MAI) removal using a spreading code having good cross-correlation characteristics at the time of synchronization.
However, in a wireless network without a center, there are two problems:
on one hand, the whole network synchronization is difficult to realize, under the asynchronous condition, the multiple access interference among all channels is very large, for example, walsh codes are adopted, the cross correlation is very poor, and under the asynchronous condition, the mutual interference is very large. The Gold code is adopted, the maximum cross-correlation value is improved, but the MAI is increased along with the increase of channels, and the cross-correlation is 17/127 (normalized value) which is close to 1/7 in the 127-bit Gold code as an example, and the processing gain is obviously not large enough. m-sequences have a single autocorrelation peak, i.e., the autocorrelation is good, but the cross-correlation between different m-sequences is not good. The best cross-correlation sequence is actually the preferred pair, with cross-correlation properties identical to those of the Gold code. As in the previous example, taking the 127-bit sequence as an example, the maximum cross-correlation value is 17/127. It can be seen that when using Walsh, gold codes or different m-sequences for a centerless communication network, the multiple access interference MAI between channels is still large under unsynchronized conditions.
On the other hand, it is difficult to find a code group consisting of a sufficient number of spreading codes, and the cross-correlation performance between each two spreading codes is good. Furthermore, a centerless wireless network is almost impossible to achieve full network clock synchronization, so that Walsh, gold, and m sequences cannot be used to achieve code division. It is known that finding a spreading code with good autocorrelation, i.e. with a single correlation peak, and with good linear and cyclic correlation, is easier than finding a single such spreading code than finding multiple code groups with good pairwise cross-correlation. Such as barker codes, m-sequences and specific spreading codes with zero correlation property, etc., all have good autocorrelation performance. As an example of an m-sequence: the m sequence has good autocorrelation, and any m sequence PN (t) and the phase-shift sequence PN (t-k tau) of the m sequence c ) BetweenAs long as k τ is cross-correlated c Greater than one chip slot, the value is-1/N. With this characteristic, a code division channel can be realized.
In the existing centerless wireless networks (such as Ad hoc and sensor networks) adopting spread spectrum technology, one is to adopt a single spread spectrum channel in a physical layer and adopt an 802.11 DCF protocol in an access layer, and the system does not fully utilize the advantages of spread spectrum code division to realize multiple channels and has low network throughput. Another type is a centerless wireless network that uses spread spectrum code division to implement multiple channels, but where nodes in the network are all assigned a fixed spreading code. A block diagram of a multi-channel spread spectrum communication system suitable for a wireless network is shown in fig. 1 or fig. 2:
the access method of the multichannel spread spectrum communication system suitable for the centerless wireless network comprises the following steps: when a source node comprising the system has data to transmit, the data is firstly transmitted in a common channel C 1 Sends request packet RTS on, all idle nodes are in C 1 Waiting on the channel, i.e. using spreading code C 1 And performing despreading processing. Destination node is at C 1 After receiving RTS information of a sending request packet on the channel, the RTS information is also on a common channel C 1 And sends a response packet CTS to the source node. The RTS packet includes information such as a source node identification address (or address) ID, a destination node identification address ID, and a channel number to be used for transmitting the data packet. The response packet CTS contains information such as a destination node identification address ID, a source node identification address ID, and a channel number for transmitting a data packet. When the source node receives the response packet CTS sent by the destination node, the source node switches to the selected channel C i Transmitting data packets upwards, i.e. using spreading codes C i And carrying out spread spectrum modulation on the data. At the same time, after the destination node sends the response packet CTS on the public channel, it immediately transfers to the channel C according to the channel number reported by the sending request packet i Receive on, i.e. using spreading code C i The received signal is subjected to a correlated despreading process. After the destination node correctly receives the data packet, i.e. in the same channel C i An acknowledgement packet ACK is sent up. The source node is in the same channel C after sending out the data packet i And receives an acknowledgement packet of the destination node. All other nodes receiving Request To Send (RTS) or response to send (CTS) packets on a common channel automatically place them on the corresponding channel (C) i And performing back-off, wherein the back-off duration is determined by the duration of the data packet, the duration of the response packet CTS, the protection time slot and the like, so that the system completes one-time access. The spread spectrum communication systemThe system may implement dynamic allocation of channels (DCA).
When the spread spectrum communication system realized by adopting the method shown in fig. 2 is applied to a centerless wireless network, the functional principle of the spread spectrum communication system is the same as that of the system. The spread-spectrum communication system shown in fig. 2 differs from the spread-spectrum communication system described in fig. 1 in that: the spread spectrum communication system illustrated in FIG. 2 employs m and C 1 ……C m And the frequency spreading codes respectively correspond to matchers to realize despreading. The spread-spectrum communication system shown in fig. 2 is complex and bulky in hardware implementation.
The matcher in the system shown in fig. 2 is shown in fig. 3. The matcher in the system shown actually performs the following operations:
Figure C20051002823600071
wherein { a } i I is more than or equal to 0 and less than or equal to N-1 is a local coefficient sequence, x i "0. Ltoreq. I.ltoreq.infinity" is a received sequence, and R (n) represents a correlation value obtained by calculation. Coefficient sequence a i The value is { + -1 }, and the receiving sequence is a quantization value sequence after A/D conversion.
When the two spread spectrum communication systems are applied to a centerless wireless network, the defects are as follows:
(1) In case the network cannot achieve full network clock synchronization, C is assumed 1 ……C m In the spread spectrum code set, the cross correlation between every two spread spectrum codes is good. As previously mentioned, this is difficult to achieve in practice.
(2) Collisions between common and data channels remain unavoidable due to the mobility of the centerless wireless network.
(3) The selection of the channel for transmitting data is selected by the source node, and the status of each channel in the channel status table of the destination node is not referred to, i.e. if the channel selected by the source node is busy at the destination node, access failure is inevitably caused.
(4) The hidden and exposed terminal problems remain unsolved.
(5) The function of monitoring the channel state in real time is not available.
In another conventional communication system, the system clocks of all nodes are clock signals transmitted from satellites, and a satellite receiver receives radio signals from the satellites and extracts clock signals therefrom for use as system clocks by the nodes. (see SYN-MAC: ADistributedMediumAccess control protocol for synchronized Wirelessnetworkswww.cacs.louisiana.edu Hongyi Wu， Anant Vtgikar，and Nian-Feng T z eng and ASimpleDistributedPRMAforMANETs, IEEE transactions on vehicle technology, VOL51, no2MARCH2002P 293-P305) are shown in FIG. 4. The system adopting the scheme is characterized in that all nodes in the whole network receive clock signals from satellites, and the synchronization of the sending time of the signals can be ensured. However, due to the random distribution and mobility of the nodes, the signal can not be guaranteed to reach the targetThe orthogonality of the different channels at the nodes does not completely eliminate multiple access interference.
In summary, since each node in the centerless wireless network is mobile and centerless, the network topology changes dynamically, so it is impossible to achieve the synchronization of the whole network. It is not feasible to implement multiple access in such networks directly using existing spread spectrum code division techniques. When the network is not synchronized, multiple Access Interference (MAI) between channels is severe. So, currently, in a wireless network without a center, the physical layer adopts a single channel of a spread spectrum technology, and the access layer adopts an 802.11 DCF protocol. If a multi-code spread spectrum code division technology is adopted to realize multiple access channels, because of no central control, each mobile node cannot know the channel use state of the whole network, a Dynamic Code Allocation (DCA) mechanism cannot be realized, and the application of the spread spectrum technology in a wireless network is greatly limited.
Disclosure of Invention
The invention aims to provide a spread spectrum communication system for realizing code division multiple access by using different phase sequences of a single spreading code, so that a plurality of mobile nodes realize code division multiple access (namely multiple channels) under the condition of no central control, namely the establishment of links of any two nodes is realized. A plurality of node pairs (one node pair is a pair of transceiving nodes) carry out spectrum spreading on a data signal by using different phase sequences of the same spreading code, and the nodes all use a data clock provided by a satellite, so that the transmission time of one-bit signals of different nodes in the coverage area of one node is basically synchronous, and the same-channel interference can not occur at a destination node as long as the path delay difference from the node to the destination node in the coverage area is smaller than the delay of an adjacent phase sequence. Therefore, the wireless signals with the same frequency band can be used for carrying out communication between every two wireless signals at the same time, the network throughput is improved, and the multiple access interference is reduced.
Another objective of the present invention is to provide a centerless wireless network using a spread spectrum communication system, wherein different channels use different phase sequences of the same spreading code, so that each node in the centerless network using the spread spectrum communication system can autonomously monitor the channel usage in its coverage area, thereby automatically implementing channel dynamic allocation (i.e. automatically selecting an idle spreading code) and avoiding collision.
In order to achieve the above purpose, the idea of the invention is that:
the invention provides a Dynamic Code Allocation (DCA) mechanism for reducing multiple access interference in a centerless wireless network. The basic idea is that all mobile nodes receive a radio signal of a certain satellite and extract a clock from the received radio signal as a data clock of the node. The adopted spread spectrum code set is composed of different phase sequences of a single spread spectrum code, and because a uniform data clock is adopted, the transmission time of the spread spectrum signal transmitted by the nodes in the coverage area of one node is synchronous, and as long as the path delay difference from the nodes to the target node in the coverage area is less than the delay of the adjacent phase sequences, the same-channel interference can not occur.
Since all nodes receive the satellite's radio signal and extract the clock from it as the data clock. Is divided intoIt can be known that the path difference of the satellite signal to two mobile nodes with any distance r
Figure C20051002823600091
And R is the height of the satellite from the ground. Taking the node coverage area of the centerless wireless network as 300 meters, the satellite is a low orbit satellite (R =300 Km) as an example. d is approximately equal to 0.15 meter, and time delay of two paths
Figure C20051002823600092
The maximum time difference between the arrival of the signal at the destination node by any of nodes a and C, both within the coverage area of the destination node, will not exceed 1ns. If the data speed is 1Mbps, a 63-bit m-sequence spread spectrum code is adopted, then T c And the delay of the path has little influence on the delay of the spread spectrum signal in a certain coverage area, and only occupies 1/16 of one Chip time slot. Therefore, in a wireless network without a center, the transmission time of the spread spectrum signals of two nodes in the coverage area of any node is synchronous, and as long as the spreading codes have small cross-correlation values under a condition of small time delay (for example, the phase shift of m sequences is larger than the cross-correlation value between sequences of one chip), the Multiple Access Interference (MAI) caused by each other is small, and different mobile nodes can completely receive the data information transmitted by the channel corresponding to the required phase sequence. More importantly, all mobile nodes adopt different phase shift sequences of the same spreading code as the spreading code, so that a single node can detect the states of all channels, and a centerless Dynamic Code Allocation (DCA) mechanism is realized.
The invention relates to a wireless network adopting spread spectrum technology, in particular to a centerless wireless network, wherein the network consists of a plurality of mobile nodes, and other nodes in the coverage area of one node can carry out half-duplex communication (time division duplex (TDD) mode) with the node; nodes outside the coverage area of one node cannot communicate with the node, and the communication between the nodes must be forwarded by other nodes.
Fig. 5 is a diagram of a network architecture for a spread-spectrum communication system employing the present invention. The nodes 100 in the figure comprise the spread spectrum communication system of the present invention, i.e. all nodes have the same software and hardware. All nodes communicate by adopting the spread spectrum communication system.
According to the inventive concept, the invention adopts the following technical scheme:
a spread spectrum communication system for code division multiple access comprising:
a matching unit for receiving radio signals, the output of which is multi-path related data, connected to a related multi-path selecting unit and a control processing unit; the related multi-path selection unit outputs the related data value in the appointed time slot to a demodulation unit under the control of the control processing unit;
the demodulation unit demodulates the baseband information carried by the relevant data of the appointed time slot, and the output of the demodulation unit is connected to the control processing unit;
a duplexer connected with the control processing unit, the matching unit, an antenna and a spread spectrum modulation unit and used for completing the transceiving conversion under the control of the control processing unit;
the spread spectrum modulation unit is connected with a code multipath selection unit and the control processing unit, and expands the narrow-band low-rate data signal into a wide-band signal; when the system sends a control packet, under the control of the control processing unit, selecting a phase sequence of a spreading code corresponding to a common channel to output; when sending data packet, selecting spreading code phase sequence appointed by both sending and receiving parties to output.
The control processing unit controls the related multi-path selection unit, the demodulation unit, the duplexer and the spread spectrum modulation unit.
It is characterized in that the method also comprises:
a satellite receiving clock extraction unit is connected with an antenna, a clock synchronization unit, the control processing unit, a control time sequence generation unit and a spread spectrum code group generator, receives wireless signals sent by a satellite, and extracts a clock from the wireless signals as a data clock of the spread spectrum communication system;
the clock synchronization unit generates a spread spectrum code clock, the length of the spread spectrum code is N, and then a data clock period Td and a spread spectrum code chip period T C The relation between them is T d ＝NT C I.e. to ensure the synchronization relationship between the data and the spreading codes;
the spread spectrum code group generator is connected with the code multipath selection unit, and the generated spread spectrum code is a barker code, an m sequence or a code sequence with good autocorrelation performance. The output is a code set formed by the spreading codes and their phase sequences.
The time sequence generating unit is connected with the control processing unit and generates a time sequence signal corresponding to a channel.
The core of the control processing unit is a CPU processor, which reads the assigned correlation value of the assigned time slot, and the size of the correlation value in the assigned time slot represents the busy state of the channel; judging the magnitude of the correlation value in the appointed time slot, wherein if the magnitude exceeds a certain threshold value, the corresponding channel is busy, and if the magnitude is lower than a given threshold value, the channel is idle; storing the result in a channel table, and dynamically updating the result; meanwhile, the unit stores a Media Access Control (MAC) protocol; under the control of the control processing unit, the demodulation unit only demodulates the information of the common channel when being idle; when a mobile node needs to send data, after the negotiation between the mobile node and the mobile node is completed on a common channel, sending data information on a channel appointed by the negotiation; selecting a spreading code phase sequence corresponding to a public channel when a control packet is sent; when sending data packet, selecting spreading code phase sequence negotiated by both sides; the control processing unit receives the data sent by the demodulation unit and processes the data by an upper layer program; the control processing unit also performs: the duplexer is controlled to complete the receiving and transmitting conversion, control the selection of the spread spectrum code and control the selection of the multipath related output.
The spread spectrum communication system for realizing code division multiple access by adopting different phase sequences of a single spread spectrum code is characterized in that different phase sequence sets of the spread spectrum code are used for forming a spread spectrum code set; spreading codes PN (t), PN (t-tau) 0 )……PN(t-kτ 0 ) Wherein the value of k should satisfy (k + 1) tau 0 ＜NT C (ii) a And N is the code length.
The spread spectrum communication system for CDMA by using different phase sequences of single spreading code is matched with correlationThe unit outputs multipath and spread spectrum codes PN (t), PN (t-tau) 0 )……PN(t-kτ 0 ) Matching correlation values R0, R1, R2 0 The time delay of two adjacent phase sequences in a spreading code set.
The spread spectrum communication system for realizing code division multiple access by adopting the different phase sequences of the single spread spectrum code has the advantages that as the system uses the single spread spectrum code, the different phase sequences of the spread spectrum code represent different channels, a matching unit 107 can be used for receiving spread spectrum signals, the output of the spread spectrum signals is a multi-channel correlation value, and the reading judgment of the pulse values of the correlation peaks of each channel of different time slots represents the detection of busy and idle states of different channels; if a certain threshold is exceeded, the corresponding channel is busy; below a certain threshold indicates that the channel is in an idle state;
the matching unit, the spread spectrum code group generator and the control time slot generating unit are realized by adopting a field programmable gate array FPGA integrated chip or a special integrated circuit ASIC.
A wireless network without center of the spread spectrum communication system is composed of multiple mobile nodes, each mobile node is set with a spread spectrum communication system using different phase sequences of single spread spectrum code to realize CDMA.
The centerless wireless network is characterized in that each mobile node receives a radio signal of the same satellite and extracts a clock from the radio signal as a data clock of the system.
Said is free ofCentral wireless network, coverage area radius r of a mobile node and time delay tau of two adjacent phase sequences in spread spectrum code set 0 The following relations exist between the following components: r < C tau 0 Where C is the speed of light, τ 0 Is the time delay of the adjacent phase sequence. I.e., the coverage area with the radius of r, each mobile node can correctly receive the information transmitted by the spread spectrum communication system. Outside the coverage area, the information transmitted by the spread spectrum communication system cannot be correctly received.
In the centerless wireless network, each mobile node can monitor the use condition of all spread spectrum channels, so that the wireless network consisting of a plurality of mobile nodes can dynamically allocate channels under the condition of no central station; the specific distribution mechanism is as follows: a mobile node having a data packet to be transmitted transmits a request-to-transmit packet on a common channel, the packet including an identification address ID of a transmitting node, an identification address ID of a receiving node, and a channel state table of the transmitting node. After receiving the request packet on the public channel, the destination mobile node compares the channel state table of the sending node with the channel state table of the destination mobile node, randomly selects an idle channel, and then sends a response packet on the public channel, wherein the response packet comprises a sending node identification address ID, a destination node identification address ID and a selected channel number. After receiving the response packet, the sending node sends a confirmation packet on the public channel, wherein the confirmation packet should contain the identification address ID of the sending node, the identification address ID of the receiving node and the channel number. Then the transmitting node transfers to the corresponding channel to transmit the data packet. After receiving the acknowledgement packet on the common channel, the destination node switches to the corresponding channel to receive the data packet; after receiving, the destination node sends the acknowledgement packet on the same channel.
In a wireless network including a plurality of mobile nodes, the data clock of each node is substantially the sameTherefore, m-sequences or other different phase sequences of the spreading codes with single autocorrelation peak can be adopted to form a set of spreading code sets for multi-node sharing. The specific implementation method comprises the following steps: the spreading code PN (t) has a code set composed of different phase sequences: PN (t), PN (t-tau) 0 )，PN(t-2τ 0 )……PN(t-Kτ 0 ). Where k τ is 0 ＜NT C 。τ 0 Is T C Integer multiple of, i.e. τ 0 ＝JT C . So the number of codes in the code set is I = [ N/J =]And (4) respectively. J is selected and the coverage area radius r of a single node is less than C tau 0 (or transmit power). If the coverage area is large, J should be increased appropriately to ensure that the spread spectrum signals made by any two nodes within the coverage area of one node are not the same at the receiving node due to path delay, i.e., co-channel interference is not caused.
The invention can enable a single node to monitor all channels in real time. Because the whole network uses single spread spectrum code, and uses its different phase-shift sequences to represent different channels, so that it can use a matching network to output multi-channel related data, and the appearance of related peak in the appointed time slot can represent that the correspondent channel (phase-shift sequence) is busy, and when there is no related peak or its related peak value is lower than set threshold, it can represent that the correspondent channel is in idle state. And simultaneously, each node also detects the upper limit value of the correlation peak, and when the upper limit value is larger than a threshold, namely the two nodes are close to each other and enter the multiple access interference area of the other side, the situation that one node receives and one node receives the two nodes at the same time is avoided.
The invention also includes: each node is stored with a channel state table, and the state table stores the busy and idle states of each channel. And selecting idle channels when the node carries out multiple access.
Each node also comprises a distance table between the node and the adjacent node, and the table stores the size of the relevant peak value of the adjacent node signal monitored by the node. When the correlation peak is larger than a threshold, it means that the two points are very close to each other and may enter the MAI interference region of the other. At this point, if one party is receiving signals (communications), the other party should avoid (back-off) and avoid multiple access interference.
The code division multiple access method of each node is as follows: each node performs Dynamic Code Allocation (DCA). When some node has data to be sent, the node completes CSMA/CA access on a common channel (for example, using PN (t) to perform spread spectrum), if the channel is busy, the node randomly backs off, if the back-off time is up, the node continues to detect, if the channel is still busy after a time slot, the node continues to back off, otherwise, the node sends a request packet. All idle nodes watch on the common channel. The request packet includes a transmitting node identification address ID, a destination node identification address ID, and a transmitting node idle channel number. After receiving the request packet sent to the destination node, the destination node detects the idle channel number of the sending node, selects a channel number with idle receiving and sending parties according to the channel state information of the destination node, and puts the channel number into a response packet sent by the destination node. And after receiving the response packet of the destination node, the transmitting node transmits an acknowledgement packet (ACK), wherein the ACK packet contains the channel number of the selected transmitting channel.
If the destination node is not in the coverage area of the sending node, the receiving node carries out route discovery according to a route protocol. The adjacent nodes of the sending node and the destination node wait on the idle channel, detect the RTS of the sending request packet, respond to the CTS of the packet and confirm the ACK of the packet, and retreat on the channel selected by the sending and receiving parties.
And after the ACK packet of the acknowledgement packet is sent, the sending node transfers to the selected channel to send the data packet, and the destination node transfers to the selected channel to receive the data packet. After completing the reception of the data packet, the destination node sends an acknowledgement packet in the selected channel and releases the channel.
Compared with the prior art, the invention has the following obvious substantive characteristics and remarkable advantages:
(1) The invention adopts single spread spectrum code, and is easier to search single spread spectrum code with good autocorrelation than to search a plurality of code groups with good pairwise cross correlation performance, simple to realize and less interference of channel access.
(2) The multi-channel access is easy to realize, and the network throughput is high.
(3) The node has the function of monitoring the channel state in real time.
(4) Because different channels use different phase sequences of the same spreading code, each node can realize channel dynamic allocation (namely self-selecting idle spreading codes) and avoid collision.
(5) The node can monitor the use condition of the channel in real time, thereby solving the problems of hiding the terminal and exposing the terminal.
Drawings
Fig. 1 is a schematic diagram of a conventional multi-channel spread spectrum communication system suitable for a wireless multi-hop network.
Fig. 2 is a schematic diagram of another conventional multi-channel spread spectrum communication system suitable for a wireless multi-hop network.
Fig. 3 is a schematic diagram illustrating the configuration of a matcher in a conventional system.
Fig. 4 is a schematic diagram of a system using a satellite clock.
Fig. 5 is a schematic diagram illustrating the composition of a centerless wireless network.
Fig. 6 is a block diagram of a spread spectrum communication system implementing code division with different phase sequences of a single spreading code.
Fig. 7 shows a schematic diagram of the spreading code group generator.
Fig. 8 is a schematic diagram showing the configuration of the matching unit.
Fig. 9 is a diagram showing the composition of a control slot generation unit.
Fig. 10 shows a control slot signal diagram.
Detailed Description
A preferred embodiment of the present invention is described in detail below with reference to the accompanying drawings:
fig. 5 shows a centerless wireless network implementing code division multiple access with different phase sequences of a single spreading code. A and B, C and D are adjacent nodes and communicate with each other. H and E are adjacent nodes of A, but are in an idle state and have no data transmission. Except for H, B, E, other nodes are outside the coverage area of the node a, and cannot directly receive the data packet sent by the node a, and can only forward the data packet through other nodes, such as the data packet forwarded by the node B to the node O in the example of fig. 1. In a typical centerless wireless network, E and F are not able to communicate simultaneously. In the present invention, E and F can communicate on different channels simultaneously.
Fig. 6 is a block diagram of a spread spectrum communication system of a node. The system mainly comprises a satellite receiving clock extraction unit, a Chip clock synchronization unit, a PN code generator, a time sequence control unit, a spread spectrum modulation unit, a shaping circuit, a high-frequency front-end circuit, a duplexer, a control processing unit, a matching receiving unit, a channel detection unit and the like.
The specific structure of a spread spectrum communication system is described as follows:
(1) The radio signal received by the satellite receiving antenna 112 is sent to the satellite receiving clock extracting unit 101, and the unit extracts a clock as a data clock from the radio signal transmitted from the satellite. The clocks are simultaneously sent to one input terminal of the clock synchronization unit 102, the control timing generation unit 111, the PN code group generator 103, and the control processing unit 110.
(2) The clock synchronization unit 102 is composed of a phase detector 102-1, a low pass filter 102-2, a voltage controlled oscillator 102-3, and a 1/N frequency divider 102-4, as shown in the dashed box of fig. 6. The data clock is coupled to an input of the phase detector 102-1, the output of which is provided to the input of the low pass filter 102-2. The output of the low pass filter 102-1 is fed to a voltage controlled oscillator 102-3. The output of the voltage controlled oscillator 102-3 is a chip clock signal, which is supplied to one input of the PN code group generator, the control timing generation unit, and the control processing unit, respectively. While the other of the voltage controlled oscillators 102-3 is fed to the input of the 1/N divider 102-4 whose output is fed to one input of the phase detector 102-1. Thus, the phase detector 102-1, the low pass filter 102-2, the voltage controlled oscillator 102-3, and the 1/N frequency divider 102-4 form a phase locked loop that outputs the period T of the chip clock pulse c For input data clock period T d one-N times lower.
(3) Spread spectrum code set generator 103 generates a set of spread spectrum code phase sequences { PN (t), PN (t-tau) 0 )，……PN(t -kτ 0 ) And k +1 outputs thereof are respectively supplied to one input terminal of the code multiplexing selection unit, and the other control input bus is connected to the control processor 110. Under the control of the control processor 110, the code multiplexer 104 selects a specific phase sequence from the set of spread phase sequences to output.
(4) An input terminal of the spread spectrum modulation unit 105 controls the data output of the processing unit 110, and an input terminal thereof controls the output of the code multiplexing unit 104. The spread spectrum modulation unit 105 completes spread spectrum modulation of data, and outputs a pulse signal that is N times higher than the data pulse rate after the spread spectrum modulation.
(5) The duplexer 106 is connected to an antenna 113 with one input for the signaling signal and one output for the received signal, and an input control is connected to a control output of the control processing unit 110. The TDD mode transceiving conversion is completed under the control of the control processing unit 110.
(6) The input of the matching unit 107 is a sampled sequence signal of the received analog signal, and the output thereof is a (k + 1) -path matching correlation data sequence R 0 ……R k The (k + 1) outputs are respectively connected with the related multi-path selection unit 108And (k + 1) inputs to control processing unit 110.
(7) The (k + 1) inputs of the related multi-path selection unit 108 are connected to the (k + 1) related outputs of the matching unit, respectively, one control input terminal thereof is connected to one output control terminal of the control processing unit 110, and the other (k + 1) output control terminals are connected to the (k + 1) control time slot outputs T of the control time slot generation unit 0 ……T k Are connected. Under the control of the control processing unit 110 and the corresponding control slot, the correlation multiplexing unit selects a correlation output at the time of specifying the slot.
(8) The input of the demodulation unit 109 is connected to the output of the correlation multiplexing unit. The demodulation output of the demodulation unit 109 is connected to the data input of the control processing unit.
(9) One input of the control timing generation unit 111 is connected to the data clock output of the satellite reception clock extraction unit, and one input thereof is connected to the chip clock output of the clock synchronization unit. The output is (k + 1) control time slot signals T 0 ……T k And are respectively sent to the relevant multiplexing unit 108 and the control processing unit 110. The detailed description of the control timing generation unit 111 follows.
(10) The connection of the control processing unit 110 to the other units is as described above. Under the control of this unit, when data is transmitted, the code set { PN (t), PN (t- τ) { PN (t) } from the PN code group generator is output from the code multiplexing unit 104 0 )，…… PN(t-kτ 0 ) Selects a sequence to output to the spread spectrum modulation unit 105 to complete spread spectrum modulation. When in the receiving state in the present system, R is output from k +1 of the matching units by the correlation multiplexing unit 108 under the control of the control processing unit 110 0 ……R k In the first path R i At T i The data in the time slot is output to the demodulation unit 109, the demodulation unit 109 performs demodulation, and the demodulated output is sent to the control unit 110. While the control unit 110 is in one period T d Read R in sequence 0 At T 0 Data of inner, R 1 At T 1 Inner data of \8230 \ 8230; R k At T k And judging whether the data in different time slots exceed a set threshold. If the channel is busy, otherwise, it is idle, and the result is stored in a channel state table. As in R i At T i If the value in the time slot exceeds the set threshold, the ith channel is busy, otherwise, the ith channel is idle.
Fig. 7 is a schematic diagram of the structure of spreading code group generator 103 in the spread spectrum communication system for implementing code division by using different phase sequences of a single spreading code shown in fig. 6, and the implementation method is as follows:
fig. 7 is a schematic structural diagram of a spreading code group generator according to the present invention. The composition is that k J-stage shift registers are added at the output end of a general spread spectrum code generator, wherein J (k + 1) is less than or equal to N. Each J-stage shift register completes time delay shift, and one J-stage shift registerIs tau delayed by 0 ＝JT c So that the outputs of each stage are respectively PN (t), PN (t-tau) 0 )…… PN(t-kτ 0 ). The J-stage shift register is a basic constitutional unit in the figure, and is shown as a dotted frame in FIG. 7. The J-stage shift register consists of J D triggers, and the structure is as follows: the input terminal of the first D flip-flop 103-2 is connected with spread spectrumThe output end of the PN (t) of the code generator is connected with the input end of the next stage D flip-flop 103-3, and so on, the output of the J-th D flip-flop 103-4 is a phase-shifting sequence PN (t-tau) of the spreading code PN (t) 0 ). While D flip-flop 103-4 outputs PN (t-tau) 0 ) Followed by the input of the next J-stage shift register. Others may be analogized to others.
The matcher 107 shown in fig. 6 is implemented as follows:
the input sequence of the matcher shown in FIG. 8 is { x } i Is given by the sequence of coefficients { a } N-1 ，a N-2 ，…a i …a 1 ，a 0 ， a N-1 ，a N-2 ，…a N-JK The physical meaning of the input sequence is: a binary bit sequence obtained by sampling and quantizing a received signal; the physical meaning of the ordinal sequence is: representing fixed coefficients multiplied by each tap of the matched filter, which are usually 1-bit binary sequences, i.e. sequences composed of 0 and 1, when the coefficients multiplied by the taps are 0, it means that the corresponding multipliers can be omitted, and the matcher implementing method includes the following steps:
(1) The input sequence is driven by a clock signal from x 0 Initially, it is sent to delay unit 107-1 in sequence.
(2) And all signals passing through the delay units of all stages are simultaneously sent to one input end of all specific coefficient multipliers through a data bus.
(3) And the other input end of each multiplier is respectively fed with each specific coefficient corresponding to the matcher. Namely a N-1 Is fed to one input of a first stage multiplier 107-6, a N-2 To an input of a second stage multiplier 107-7, and so onPush away, a 0 To one input of the nth stage multiplier 107-8. Starting from the N +1 th multiplier, the coefficient of one input is again a N-1 ，a N-2 Sending the signal into an input end of an N + 2-level multiplier, and so on, wherein an input end of an N + JK-level multiplier is a N-JK . Therefore, the matcher has N + JK-level delay units in total.
(4) The multiplication operations of the multipliers are performed, and the obtained results are simultaneously and correspondingly provided to one input end of the addition network 107-11, namely y N-1 ，y N-2 ，…y 0 ，z N-1 ，z N-2 ，…z N-JK Respectively, to one input of the summing network 107-11.
(5) The summing network has k outputs, the summation of which is in turn:
Figure C20051002823600161
Figure C20051002823600162
Figure C20051002823600163
Figure C20051002823600171
1≤j≤k
namely R 0 Corresponding to PN (t) = { a = 0 ，a 1 …a N-1 The spreading code match output of R 1 Corresponding to PN (T-T) 0 )＝ PN(t-JT c )＝{a N-J ，a N-J+1 …a N-1 ，a 0 ，a 1 …a N-J-1 The matched output of J is cyclically shifted J, and so on.
The control timing generation unit 111 included in the spread spectrum communication system is implemented as follows:
the control slot generating unit shown in fig. 9 outputs a chip clock pulse T c The other input of which is a data clock pulse T d . Data clock T d The rising edge of (c) clears N-ary counter 111-1. N-ary counter 111-1 versus input chip clock T c Counting is carried out, and the output is the carry terminal C of the N-system counter. The basic constituent unit of the control timing generation unit is a J-stage shift register and or circuit, which is shown in a dashed box in fig. 8. The basic building block is constructed as follows: the input of the first basic component unit is connected with the carry bit C of the N-system counter, that is, the input of the first D flip-flop 111-2 is connected with the carry bit C of the N-system, the output thereof is connected with the input end of the 2 nd D flip-flop 111-3, and so on, the input of the J-th D flip-flop 111-4 is connected with the output end of the J-1 stage D flip-flop, the output thereof is connected with the input end of the next basic component unit, and so on. The clock input CP of all shift registers is connected with the chip clock pulse T c . Control time slot TS 0 This results in: j inputs of the OR gate 111-5 are connected to the input terminals T of J D flip-flops of the first stage J shift register shown in the figure 1 ， T 2 ……T J . Control time slot TS 1 ……TS k And so on. The time slot signal and chip clock pulse T generated by FIG. 8 c Data time slot T d The corresponding relationship is shown in fig. 9.

Claims (9)

1. A spread-spectrum communication system for code division multiple access, comprising:
a matching unit (107) for receiving the radio signal, the output of which is multipath correlated data; is connected to a relevant multiplexer unit (108) and a control processing unit (110); the related multiplexer (108) outputs the related data value in the appointed time slot to a demodulator (109) under the control of the control processing unit (110);
the demodulation unit (109) demodulates baseband information carried by the relevant data of the appointed time slot, and the output of the demodulation unit is connected to the control processing unit (110);
a duplexer (106) is connected with the control processing unit (110), the matching unit (107), an antenna (113) and a spread spectrum modulation unit (105), and finishes the transceiving conversion under the control of the control processing unit (110);
the spread spectrum modulation unit (105) is connected with a code multiplexing unit (104) and the control processing unit (110) and spreads the narrow-band low-rate data signal into a wide-band signal; when the system sends a control packet, under the control of the control processing unit (110), selecting a phase sequence of a spreading code corresponding to a common channel to output; when sending data packet, selecting spreading code phase sequence appointed by both sending and receiving parties to output;
the control processing unit (110) controls the related multiplexing unit (108), the demodulation unit (109), the duplexer (106) and the spread spectrum modulation unit (105);
it is characterized in that the method also comprises:
a satellite receiving clock extraction unit (101) is connected with an antenna (112), a clock synchronization unit (102), the control processing unit (110), a control time sequence generation unit (111) and a spread spectrum code group generator (103), receives wireless signals transmitted by a satellite, and extracts a clock from the wireless signals as a data clock of the spread spectrum communication system;
the clock synchronization unit (102) is connected with the spread spectrum code group generator (103), the control processing unit (110) and the control time sequence generation unit (111) to generate a spread spectrum code clock, the length of the spread spectrum code is N, and then the data clock period Td and the spread spectrum code chip period T are C The relation between them is T d ＝NT C I.e. to ensure the synchronization relationship between the data and the spreading codes;
the spread spectrum code group generator (103) is connected with the code multipath selection unit (104), the generated spread spectrum code is a barker code, an m sequence or a code sequence with good autocorrelation performance, and the output of the spread spectrum code group generator is a code set formed by the spread spectrum code and a phase sequence thereof;
the control time sequence generating unit (111) is connected with the control processing unit (110) and generates a time sequence signal corresponding to a channel;
the core of the control processing unit (110) is a CPU processor, and reads the assigned correlation value of the assigned time slot, and the size of the correlation value in the assigned time slot represents the busy or idle of the channel; judging the magnitude of the correlation value in the appointed time slot, if the magnitude exceeds a certain threshold value, indicating that the corresponding channel is busy, and if the magnitude is lower than a given threshold value, indicating that the channel is idle; storing the result in a channel table, and dynamically updating the result; meanwhile, the unit stores a media access control protocol; under the control of the control processing unit (110), a demodulation unit (109) is enabled to demodulate only the information of the common channel in idle time; when a mobile node needs to send data, after the negotiation between the mobile node and the mobile node is completed on a common channel, sending data information on a channel appointed by the negotiation; selecting a spreading code phase sequence corresponding to a public channel when a control packet is sent; when sending data packet, selecting spreading code phase sequence negotiated by both sides; the control processing unit (110) receives the data sent by the demodulation unit 109 and carries out upper-layer program processing; the control processing unit (110) further performs: the control duplexer (106) completes the receiving and transmitting conversion, controls the selection of the spreading codes and controls the selection of the multipath related output.
2. The spread-spectrum communication system for code division multiple access according to claim 1, wherein the set of spreading codes is formed using different sets of phase sequences of the spreading codes; spreading codes PN (t), PN (t-tau) 0 )……PN(t-kτ 0 ) Wherein the value of k should satisfy (k + 1) τ 0 ＜NT C (ii) a N is the code length, τ 0 The time delay of two adjacent phase sequences in a spreading code set.
3. The spread-spectrum communication system for code division multiple access of claim 2, wherein: the matching correlation unit 107 outputs a plurality of pathsWith spreading codes PN (t), PN (t-tau) 0 )……PN(t-kτ 0 ) R0, R1, R2.. Rk are matched.
4. The spread spectrum communication system according to the cdma of claim 1, wherein a matching unit (107) is used to receive the spread spectrum signal, the output of which is a plurality of channels of correlation values, and the reading of the pulse values of the correlation peaks of each channel of different timeslots is determined to represent the detection of busy/idle states of different channels; if a certain threshold is exceeded, the corresponding channel is busy; below a certain threshold indicates that the channel is in an idle state.
5. The spread spectrum communication system according to the cdma of claim 1, wherein the matching unit (107), the spreading code group generator (103), and the control slot generating unit (111) are implemented as FPGA (field programmable gate array) integrated chips or ASIC (application specific integrated circuit).
6. A centerless wireless network employing a spread spectrum communication system of code division multiple access as defined in claim 1 consisting of a plurality of mobile nodes (100), wherein each mobile node (100) is configured with one of said spread spectrum communication systems implementing code division multiple access using different phase sequences of a single spreading code.
7. A centerless wireless network as claimed in claim 6, characterized in that each mobile node (100) receives radio signals of the same satellite and extracts a clock therefrom as the system's data clock.
8. The centerless wireless network of claim 6 wherein the coverage area of one mobile node is one halfRadial r and time delay tau of two adjacent phase sequences in spread spectrum code set 0 The following relations exist between the following components: r < C tau 0 Where C is the speed of light, τ 0 Is the time delay of the adjacent phase sequence; i.e. the footprint with radius rEach mobile node can correctly receive the information sent by the spread spectrum communication system; outside the coverage area, the information transmitted by the spread spectrum communication system cannot be correctly received.
9. The centerless wireless network of claim 6 wherein each mobile node (100) is capable of monitoring the usage of all spread spectrum channels, so that a wireless network consisting of multiple mobile nodes can dynamically allocate channels without a central station; the specific allocation mechanism is: a mobile node which has a data packet to be sent sends a request sending packet on a common channel, wherein the packet comprises an identification address ID of a sending node, an identification address ID of a receiving node and a channel state table of the sending node; after receiving the request packet on the common channel, the destination mobile node compares the request packet with the channel state table of the destination mobile node according to the channel state table of the transmitting node, randomly selects an idle channel, and then transmits a response packet on the common channel, wherein the response packet comprises a transmitting node identification address ID, a destination node identification address ID and a selected channel number; after receiving the response packet, the sending node sends a confirmation packet on the public channel, wherein the confirmation packet contains a sending node identification address ID, a receiving node identification address ID and a channel number; then the sending node transfers to a corresponding channel to send a data packet; after receiving the confirmation packet on the common channel, the destination node switches to the corresponding channel to receive the data packet; after receiving, the destination node sends the acknowledgement packet on the same channel.
CNB2005100282367A 2005-07-28 2005-07-28 Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code Expired - Fee Related CN100365945C (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CNB2005100282367A CN100365945C (en) 2005-07-28 2005-07-28 Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code
PCT/CN2006/001898 WO2007012289A1 (en) 2005-07-28 2006-07-28 Spread spectrum communication system and decentralized control wireless network for implementing cdma through application of a single spread spectrum code having different phase sequences

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CNB2005100282367A CN100365945C (en) 2005-07-28 2005-07-28 Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code

Publications (2)

Publication Number Publication Date
CN1719741A CN1719741A (en) 2006-01-11
CN100365945C true CN100365945C (en) 2008-01-30

Family

ID=35931479

Family Applications (1)

Application Number Title Priority Date Filing Date
CNB2005100282367A Expired - Fee Related CN100365945C (en) 2005-07-28 2005-07-28 Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code

Country Status (2)

Country Link
CN (1) CN100365945C (en)
WO (1) WO2007012289A1 (en)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101114866B (en) * 2006-07-26 2010-10-06 展讯通信（上海）有限公司 Time slot synchronization method of digital non-center communication system
CN101471687B (en) * 2007-12-27 2012-10-10 中国科学院上海微系统与信息技术研究所 User terminal for wireless sensing network based on m sequence self correlation
KR20150075483A (en) * 2013-12-26 2015-07-06 엘에스산전 주식회사 Apparatus for processing intermittent message in train system
CN105588848A (en) * 2014-11-18 2016-05-18 航天信息股份有限公司 Moisture measuring apparatus and method
CN105812023B (en) * 2014-12-30 2018-05-04 弥亚微电子（上海）有限公司 Band spectrum modulation and despreading demodulation method and device based on Cross-correlations of Sample Sequences
GB2560569A (en) * 2017-03-16 2018-09-19 British Telecomm Synchronisation in a communications network
WO2018166693A1 (en) 2017-03-16 2018-09-20 British Telecommunications Public Limited Company Broadcasting in a communications network
CN110419179B (en) 2017-03-16 2020-06-16 英国电讯有限公司 Method and network for transmitting multiple signals
EP3804151A1 (en) * 2018-07-03 2021-04-14 Huawei Technologies Co., Ltd. Time interleaving code division multiple access (cdma) system for clock recovery
CN108809294B (en) * 2018-08-30 2023-11-14 北京神经元网络技术有限公司 Dynamic unit matching circuit
CN112867170B (en) * 2020-12-30 2022-08-16 南京天际易达通信技术有限公司 Sending sequence optimization method of co-location network
CN114928374B (en) * 2022-05-09 2023-06-27 北京全路通信信号研究设计院集团有限公司 Multi-access interference resistant demodulation method, device, electronic equipment and storage medium
CN117061290B (en) * 2023-10-13 2023-12-22 中国电子科技集团公司第五十四研究所 dMA and group despreading demodulation system for large number of users

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0756388A2 (en) * 1995-07-25 1997-01-29 Kabushiki Kaisha Toshiba Spread spectrum communication system
CN1238610A (en) * 1998-03-10 1999-12-15 索尼公司 Receiving method and receiver for spread spectrum signal
CN1307756A (en) * 1998-06-23 2001-08-08 艾利森电话股份有限公司 Method and apparatus for storing and accessing different chip sequences
CN2520612Y (en) * 2002-02-08 2002-11-13 西安蓝芽通信设备有限责任公司 Radio spectrum spread apparatus
US6850554B1 (en) * 1999-11-09 2005-02-01 Cypress Semiconductor Corp. Circuit and method for controlling a spread spectrum transition

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0756388A2 (en) * 1995-07-25 1997-01-29 Kabushiki Kaisha Toshiba Spread spectrum communication system
CN1238610A (en) * 1998-03-10 1999-12-15 索尼公司 Receiving method and receiver for spread spectrum signal
CN1307756A (en) * 1998-06-23 2001-08-08 艾利森电话股份有限公司 Method and apparatus for storing and accessing different chip sequences
US6850554B1 (en) * 1999-11-09 2005-02-01 Cypress Semiconductor Corp. Circuit and method for controlling a spread spectrum transition
CN2520612Y (en) * 2002-02-08 2002-11-13 西安蓝芽通信设备有限责任公司 Radio spectrum spread apparatus

Also Published As

Publication number Publication date
WO2007012289A1 (en) 2007-02-01
CN1719741A (en) 2006-01-11

Similar Documents

Publication Publication Date Title
CN100365945C (en) Spread spectrum communicatoion system and non-centre wireless network for implementing CDMA by single different phase sequence of spread spectrum code
CA2748626C (en) Random phase multiple access system with meshing
JP3472773B2 (en) Mobile station synchronization in spread spectrum communication systems.
US6912211B2 (en) CDMA to packet-switching interface for code division switching in a terrestrial wireless system
EP0639899B1 (en) Random access communication method by use of cdma, and system for mobile stations which use the method
US6801564B2 (en) Reverse link correlation filter in wireless communication systems
JP4112632B2 (en) Multi-rate direct sequence architecture using fixed division ratio and variable spreading code length
US6078607A (en) Synchronization codes for use in communication
KR101668896B1 (en) Dynamic energy control
US20090238245A1 (en) Despreading spread spectrum data
US6385187B1 (en) Device and method for generating spread spectrum signal using pseudo-orthogonal code in CDMA mobile communications system
EP1080547B1 (en) Frequency-hopping radio system with hybrid direct-sequence/frequency-hopping mode during startup
KR20010102513A (en) Method and apparatus for efficient synchronization in spread spectrum communications
JP3282518B2 (en) Spread spectrum communication system
WO2006043717A1 (en) Data block spread type spectrum spread communication method
US20050232342A1 (en) Additional hierarchical preamble for support of FDMA channel in a multi-band OFDM system
CN112020830B (en) Telegraph text signal broadcasting method and device based on phase discontinuous R-CSK modulation
KR101329059B1 (en) Apparatus and method for transmitting packet data in a wireless sensor network
US20050100079A1 (en) Pulse based communication system
US7606292B1 (en) Sub-sequence accumulation filter and method
US6504816B1 (en) Baseband signal demodulating apparatus and method in mobile radio communication system
US20030118083A1 (en) Large area wireless CDMA system and method
JPH0964884A (en) Communication system and transmitter and receiver used for the system
JPH08500230A (en) Data transmission method and CDMA / FDMA wireless system
Zhang et al. Performance analysis of multiple access protocols for cdma cellular and personal communications services

Legal Events

Date Code Title Description
C06 Publication
PB01 Publication
C10 Entry into substantive examination
SE01 Entry into force of request for substantive examination
C14 Grant of patent or utility model
GR01 Patent grant
C17 Cessation of patent right
CF01 Termination of patent right due to non-payment of annual fee

Granted publication date: 20080130

Termination date: 20100728