CN115002696A

CN115002696A - Time-limit-based non-real-time data variable-speed vertical switching method between heterogeneous networks

Info

Publication number: CN115002696A
Application number: CN202210485814.3A
Authority: CN
Inventors: 蔡家麟
Original assignee: East China Normal University
Current assignee: East China Normal University
Priority date: 2022-05-06
Filing date: 2022-05-06
Publication date: 2022-09-02
Anticipated expiration: 2042-05-06
Also published as: CN115002696B

Abstract

The invention discloses a time-limit-based non-real-time data variable speed vertical switching method between heterogeneous networks, which aims at the fact that a super-capacity cache chip is commonly configured in the conventional mobile terminal and comprehensively considers the difference between the high bandwidth of a WLAN and the low bandwidth of a cellular network, and provides a method for improving priority hopping vertical switching based on a time threshold. The method reduces the congestion level of channel occupancy in a cellular coverage area by dynamically adjusting the transmission rate of a non-real-time broadband data call between heterogeneous networks. The invention has the advantages of obviously improving the performances of UVH call loss rate of system priority, UVH call loss rate of non-priority and call blocking rate of newly-added honeycomb while keeping the integral high channel utilization rate of the system, and realizing the effective utilization of network channel resources.

Description

Time-limit-based non-real-time data variable-speed vertical switching method between heterogeneous networks

Technical Field

The invention relates to the technical field of wireless communication, in particular to a non-real-time data variable-speed vertical switching method based on time limit among heterogeneous networks.

Background

Currently, with the increasing demand of people for mobile access services, a new generation of wireless communication technology is developing towards the direction of implementing heterogeneous wireless network interworking. Cellular mobile networks and Wireless Local Area Networks (WLANs) are two major wireless communication networks in modern wireless communications. Cellular mobile networks are characterized by large coverage and low bandwidth, while WLANs are characterized by small coverage and high bandwidth. The interworking between the cellular mobile network and the WLAN can complement the advantages of the cellular mobile network and the WLAN, thereby enhancing the quality of service (QoS) of the provided service.

The process of switching connections between networks is called handover. Handovers between the same access technology networks (e.g., between WLANs) are referred to as horizontal handovers, while handovers between different access technology networks (e.g., cellular mobile networks and WLANs) are referred to as vertical handovers. Vertical handovers may be further divided into Downstream Vertical Handovers (DVHs) and Upstream Vertical Handovers (UVH). For a cellular mobile network and WLAN interworking system, DVH refers to vertical handoff from the cellular mobile network to the WLAN, and UVH refers to vertical handoff from the WLAN to the cellular mobile network. DVH is the handover procedure of the mobile user from low bandwidth large coverage to high bandwidth limited coverage network, while UVH is the handover procedure of the mobile user from high bandwidth limited coverage to low bandwidth large coverage network.

Vertical handover between heterogeneous networks is a significant challenge for seamless mobility in a new generation of mobile networks. In recent years, many handover methods for vertical handover of heterogeneous wireless networks have appeared, but these methods rarely involve vertical handover for channel preemption. T, L. Sheu et al, in 2010, in the publication "Wireless Networks" journal, an A channel prediction model for a vertical handoff in a WLAN-embedded cellular network, proposes a channel preemption vertical switching method (PMV method for short) suitable for interworking between a cellular mobile network and a WLAN, the core idea of which is: if all the effective mobile channels in the cellular mobile network are occupied, only new calls in the coverage area of the single cellular mobile network or handover calls which execute UVH procedure to handover to the coverage area of the single cellular mobile network can preempt the existing cellular mobile channels in the dual coverage areas of the cellular mobile network and the WLAN. The preempted online cellular call is forced to perform a DVH procedure with a downlink vertical handoff from the cellular mobile network to the WLAN. The PMV method effectively reduces the newly added call blocking rate and UVH handover call loss rate in the cellular mobile network. The processing mode of handover call will directly affect the quality of service (QoS) providing service to Mobile users and the performance of interworking system, and I.Katzela and M.Naghshineh were pointed out in 1996 in the paper "Channel Assignment Schemes for Cellular Mobile telecommunications Systems" published in the journal of "IEEE Personal Communications": "loss of handover calls should be avoided more than blocking of new calls within the cellular mobile network". However, in the design of how to perform cellular mobile channel occupation and preemption for the newly added call in a single-cell coverage area and the vertical handover call performing UVH handover to the single-cell coverage area, the PMV method does not consider the sequence of the two, but gives UVH handover call the same competition and right to preempt the cellular mobile channel as the newly added call, and as a result, the call loss rate performance of UVH handover call cannot be further improved. Aiming at the defects of the PMV method, An article "An uplink Priority Channel prediction Scheme for Vertical Handoff in Cellular/WLAN Interworking" proposes An uplink Priority Vertical Handoff method (referred to as UPPS method for short) suitable for a Cellular mobile network and a WLAN Interworking network in 2011 'IEEE WICOM' international conference. The method effectively improves UVH handover call drop rate performance by increasing UVH the priority of handover calls in uplink vertical handovers with channel preemption, but thereby also increases somewhat its newly added cellular call blocking rate. For limited cellular mobile channel resources, UVH handover call loss rate and newly added cellular call blocking rate are contradictory, and biasing either one will degrade the performance of the other. How to achieve the best balance between the two is always the focus of attention in the wireless communication field. M. Salamah et al, 2005 in the journal "New Trends in Computer Networks" journal paper "A Fair Bandwidth Allocation Scheme for Multimedia Handoff Calls in Cellular Networks" indicated: for the online voice call, if the call duration is short, the call drops, the user is very irritated, and when the call drops after a certain duration, the discontent emotion of the user is not strong; also, for online data calls, a user may generally tolerate dropping when the connection time is less than an acceptable range, but the dissatisfaction of the user will be quite intense when the online data transmission has been on for a significant period of time. M. Salamah et al, in the above-mentioned paper, thus propose a time-threshold channel allocation method (TTS method for short) for horizontal handover in cellular networks. The method carries out priority classification on the on-line horizontal switching call by monitoring the on-line communication time of the horizontal switching call and according to different tolerances of users to voice and data services, and aims to improve the blocking rate performance of a newly added call while ensuring that the priority horizontal switching call of a time sensitive user has lower loss rate. In IEEE WICOM' 2012 international conference, the article "a Time-threshold-based uplink Priority Scheme for Vertical Handoff in Cellular/WLAN Interworking" applies a Time threshold policy of m, Salamah et al for horizontal Handoff of the same network to Vertical Handoff between heterogeneous networks, and proposes a Time threshold-based uplink Vertical Handoff method (TUPS method for short) between heterogeneous networks, which has the advantages of maintaining the utilization rate of a system high Cellular mobile channel and lower Time-sensitive uplink Vertical Handoff call loss rate performance of a user, and obviously improving the new Cellular call blocking rate performance in the UPPS method. On the basis, an uplink Priority Hopping Vertical switching method (TPHS method for short) suitable for a Cellular mobile network and a WLAN Interworking network is proposed in a paper 'A Time-threshold-based Priority Hopping Scheme for Vertical Handoff in Cellular/WLAN Interworking' published in an international conference of 'IEEE Computer and Communications' in 2017. The method provides a priority jump algorithm aiming at the call occupation and channel preemption in the cellular coverage area on the basis of a vertical switching method based on a time threshold so as to adjust the capacity of various calls for competing for cellular mobile channels in different environments, and simultaneously, the congestion degree of the channels in the cellular coverage area is reduced by designing a DVH decision algorithm of online voice calls in a double coverage area. Nevertheless, how to further improve UVH call drop rate and new cellular call blocking rate performance is still an important goal of research. Because the mobile terminal is generally provided with a super-large-capacity cache chip at present, and the difference of high bandwidth of a WLAN and low bandwidth of a cellular network is considered at the same time, the non-real-time online broadband data call in a heterogeneous network does not need to adopt the completely same transmission rate in a single cellular coverage area and a WLAN coverage area, namely the transmission rate of the non-real-time broadband data call can be dynamically adjusted according to the characteristics of each coverage area; non-real-time broadband data is transmitted at a high rate and buffered in a mobile terminal buffer chip within a high bandwidth WLAN coverage area. Therefore, the load pressure of a single cell coverage area in a heterogeneous network can be greatly reduced, the call loss rate of the system UVH and the performance of the call blocking rate of a newly added cell can be further improved, and the use efficiency of channels in a WLAN coverage area can be improved.

Disclosure of Invention

The invention aims to provide a time-limit-based non-real-time data variable speed vertical switching method between heterogeneous networks, aiming at the defects of the prior art, and the method provides a method for improving priority jump vertical switching based on a time threshold based on the difference of bandwidth characteristics between heterogeneous networks and the fact that a mobile terminal is generally provided with a super-large capacity cache chip. The method reduces the congestion level of channel occupancy in a cellular coverage area by dynamically adjusting the transmission rate of a non-real-time broadband data call between heterogeneous networks. The invention has the advantages of obviously improving the performances of UVH call loss rate of system priority, UVH call loss rate of non-priority and call blocking rate of newly-added honeycomb while keeping the integral high channel utilization rate of the system, and realizing the effective utilization of network channel resources.

The specific technical scheme for realizing the purpose of the invention is as follows:

a non-real-time data variable speed vertical switching method based on time limit between heterogeneous networks, the heterogeneous networks are based on a cellular mobile network and a wireless local area network, the method comprises:

a) online voice and broadband data call classification

The method comprises the steps that online communication time of a call is monitored, a voice and broadband data time threshold is set according to the tolerance of a user to call drop, the voice time threshold is a time set value which is larger than the minimum call duration time acceptable by a voice user, and the broadband data time threshold is a time set value which is smaller than the maximum online data transmission time which can be tolerated by a broadband data user to drop, so that online voice and broadband data calls in a cellular coverage area are classified according to priority; online voice calls less than a voice time threshold and online broadband data calls greater than a broadband data time threshold are referred to as priority calls, while online voice calls greater than or equal to the voice time threshold and online broadband data calls less than or equal to the broadband data time threshold are referred to as non-priority calls;

b) priority algorithm for calling occupation and channel occupation in heterogeneous network cellular coverage area

According to the priority of the uplink vertical handover and the tolerance of the user to the switching call drop, UVH which has the requirement of cellular mobile channel occupation and preemption in the cellular coverage area of the heterogeneous network, namely the uplink vertical handover call and the newly added cellular call, the following priority algorithm of channel occupation and preemption is designed: when an idle cellular mobile channel exists in a cellular coverage area, the priority UVH call, the non-priority UVH call and the newly added cellular call have the same priority for occupying the channel; when no idle cellular mobile channel exists in the cellular coverage area and the preemptible cellular channel in the dual coverage area of the cellular network and the wireless local area network needs to be preempted through competition, the preemption priority of the non-priority UVH call and the newly added cellular call is reduced to the priority level lower than that of the priority UVH call, namely, the priority UVH call has stronger channel preemption capability than the non-priority UVH call and the newly added cellular call;

c) DVH decision algorithm for online voice call in dual coverage areas of heterogeneous networks

The online voice call entering the double coverage area is processed differently according to the call type defined by the voice time threshold, and the priority voice call does not actively execute the DVH process unless other calls in the single cell coverage area apply for preemption; if no idle WLAN wireless channel exists at the moment, the non-priority voice call which is allowed to enter the dual coverage area still occupies the cellular mobile channel temporarily under the condition that no cellular mobile channel is preempted, so that unnecessary offline voice is prevented from being increased;

d) non-real-time online broadband data call variable-speed transmission algorithm when heterogeneous network executes vertical switching process

Based on the difference between the high bandwidth of the WLAN and the low bandwidth of the cellular network and the fact that a super-large-capacity cache chip is generally configured on the mobile terminal, the data transmission rate of the non-real-time online broadband data call in the heterogeneous network is increased to 2 times that of the non-real-time online broadband data call in a single-cellular coverage area after the DVH process is finished; similarly, when the non-real-time online broadband data call in the heterogeneous network completes the UVH process, the data transmission rate is also reduced to half of the data transmission rate in the WLAN coverage area;

e) cellular mobile channel allocation in heterogeneous network cellular coverage areas

Total cell channel capacity in heterogeneous network ofBFor each basic bandwidth unit, as long as the remaining idle channel capacity of the current cell can meet the service requirement of a channel application call, UVH calls or newly added cell calls can occupy a cellular mobile channel.

The interworking system of the present invention has three types of cellular mobile channels: an idle cellular channel, a preemptible cellular channel and a non-preemptive cellular channel. Wherein, the preemptible cellular channel is a cellular channel occupied by a call in a dual coverage area; a non-preemptive cellular channel refers to a cellular channel occupied by a call in a single cellular mobile coverage area.

In the interworking system between cellular mobile network and wireless local area network, the online broadband data call entering the dual coverage area should perform DVH procedure as much as possible, i.e. as long as there is a free WLAN radio channel, the call abandons the cellular mobile channel and instead occupies the WLAN radio channel. However, if there is no idle WLAN radio channel, the online broadband data call entering the dual coverage area is allowed to temporarily continue occupying the cellular mobile channel even without the occurrence of the cellular mobile channel preemption, so as to avoid adding unnecessary online broadband data drops.

The obvious difference between the invention and the prior art is that the invention fully utilizes the difference between the high bandwidth of the WLAN and the low bandwidth of the cellular network, allows the non-real-time broadband data call to dynamically change the data transmission rate under different network environments, and has obvious advantages for improving the performances of the priority UVH switching call loss rate, the non-priority UVH switching call loss rate and the newly-added cellular call blocking rate in the process of executing the uplink vertical switching based on the heterogeneous network environments.

Drawings

FIG. 1 is a block diagram of a cellular mobile network and WLAN interworking system;

FIG. 2 is a simulation graph of a relationship between a call loss rate of a priority uplink vertical handover and a cellular load;

FIG. 3 is a simulation graph of the relationship between the call loss rate of non-priority uplink vertical handover and the cellular load;

FIG. 4 is a graph showing a simulation of a relationship between a blocking rate of a newly added cellular call and a cellular load;

FIG. 5 is a graph of a simulation of cellular mobile channel utilization versus cellular load;

fig. 6 is a simulation graph of WLAN radio channel utilization versus cellular load.

Detailed Description

The invention is explained in more detail below with reference to the figures and examples. The following examples are not intended to limit the invention. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept.

Fig. 1 shows a cellular mobile network/WLAN interworking system architecture, in which: single cell coverage 1, vertical handover 2 and dual coverage 3; the architecture provides voice and broadband data services to cellular mobile terminals and wireless terminals within the coverage area of the WLAN. Channel capacity of each cell in embodiment simulationBIs 20BBUs (basic bandwidth unit) and the channel capacity of each WLAN coverage area is 54 BBUs. To meet the QoS requirement of the service, a single voice call needs to occupy a channel with a basic bandwidth unit and single real-time broadband dataThe call and each non-real-time broadband data call in the single cell coverage area occupy two basic bandwidth unit channels, while each non-real-time broadband data call in the WLAN coverage area occupies four basic bandwidth unit channels. The process of generating new calls in the cell follows the Poisson process with the mean value λ c, while the process of generating new calls in the coverage area of the WLAN follows the Poisson process with the mean value λ w (where λ w is 0.04 call/s), and the performance indexes of call blocking rate and loss rate related to the present invention are mainly affected by the λ c change. The communication duration of each call follows a negative exponential distribution with an average of 6 minutes. The stay times of the online calling subscriber within a single cell and a single WLAN coverage area follow negative exponential distributions with mean values of 2 minutes and 4 minutes, respectively. The voice and broadband data time thresholds for prioritized and non-prioritized UVH calls are 120 seconds and 30 seconds, respectively.

Fig. 2, 3 and 4 show graphs simulating the relationship between the call loss rate of priority UVH, the call loss rate of non-priority UVH and the call blocking rate of newly added cells and the cell load, respectively. In fig. 2: the abscissa is the cellular call arrival rate; the ordinate is the priority UVH call loss rate; curve A is the invention, B is TPHS; in fig. 3: the abscissa is the cellular call arrival rate; the ordinate is the non-priority UVH call loss rate; curve A is the invention, B is TPHS; in fig. 4: the abscissa is the cellular call arrival rate; the ordinate is the newly added cellular call blocking rate; curve A is the invention and curve B is TPHS. According to the simulation result, the following results are obtained: compared with the TPHS method, the non-real-time broadband data variable speed transmission priority vertical switching method based on the time threshold among heterogeneous networks obviously improves the call loss rate of UVH system priority, the call loss rate of UVH non-priority and the call blocking rate performance of newly-added cells. The data transmission rate of the non-real-time broadband data call in the system is increased to one time of the original single-cell coverage area after entering the WLAN coverage area through the DVH process, so that the information transmission capacity of the non-real-time broadband data call can be completed in the WLAN coverage area as much as possible, and the congestion degree of a cellular mobile channel in the single-cell coverage area under heavy load conditions is greatly reduced; meanwhile, when the non-real-time broadband data call returns to the single-cell coverage area through the UVH process, the algorithm for reducing the transmission rate of the non-real-time broadband data call back to the standard data transmission rate of the single-cell coverage area, which is designed by the method of the invention, can ensure that the load burden of the single-cell coverage area cannot be increased by the variable-speed transmission of the non-real-time broadband data call. As can be seen from fig. 2: when the average arrival rate lambdac of newly added calls of a cellular cell reaches 0.08call/s of heavier load, the call loss rates of the priority UVH of the method and the TPHS method are respectively 0 and 7.20E-3, and the improvement degree of the method on the call loss rate of the priority UVH reaches 100 percent compared with the TPHS method; similarly, in FIG. 3, when λ c reaches 0.07call/s, the non-priority UVH call loss rates of the method and TPHS are 1.08E-2 and 2.90E-2, respectively, and the improvement degree of the method on the non-priority UVH call loss rate is 62.76% compared with the TPHS; again, as can be further seen in fig. 4: when the average arrival rate lambdac of the newly added call of the cellular cell is also 0.07call/s, the blocking rates of the newly added cellular call of the method and the TPHS method are respectively 1.75E-2 and 5.80E-2, and compared with the TPHS method, the improvement degree of the method of the invention on the blocking rate of the newly added cellular call reaches 69.83 percent, and the improvement effect is quite obvious. Fig. 5 and 6 show graphs simulating cellular mobile channel utilization and WLAN radio channel utilization versus cellular load. In fig. 5: the abscissa is the cellular call arrival rate; the ordinate is the cellular mobile channel utilization; curve A is the invention, B is TPHS; in fig. 6: the abscissa is the cellular call arrival rate; the ordinate is the utilization rate of the WLAN wireless channel; curve A is the invention and curve B is TPHS. Although fig. 5 shows the reduced cellular mobile channel utilization of the inventive method compared to the TPHS method, it is precisely this that is the design objective of the inventive method. The method greatly reduces the pressure of cellular mobile channel allocation in a cellular coverage area, and can accept more online voice calls and real-time broadband data calls in a single cellular coverage area; fig. 6 shows that the method of the present invention significantly improves the utilization of the WLAN radio channel compared to the TPHS method. Therefore, the overall channel utilization of the system is not reduced as a whole, and only a part of the channel utilization is transferred from the cellular mobile network to the WLAN network, i.e. the WLAN network shares a part of the load of the cellular mobile network.

Therefore, the analysis of the attached drawings and the examples proves that: the non-real-time data variable-speed vertical switching method based on the time limit provided by the invention can obviously improve the performances of UVH call loss rate of system priority, UVH call loss rate of non-priority and newly-added cellular call blocking rate while maintaining the utilization rate of the whole channel of the system, thereby realizing the beneficial effect of effectively utilizing channel resources.

Claims

1. A non-real time data variable speed vertical switching method based on time limit between heterogeneous networks, the heterogeneous networks refer to between cellular mobile network and wireless local area network, characterized in that the method includes:

a) online voice and broadband data call classification

According to the priority of the uplink vertical switching and the tolerance of the user to the switching call disconnection, UVH which has the requirement of cellular mobile channel occupation and occupation in the cellular coverage area of the heterogeneous network, namely the uplink vertical switching call and the newly added cellular call, the following priority algorithm of channel occupation and occupation is designed: when an idle cellular mobile channel exists in a cellular coverage area, the priority UVH call, the non-priority UVH call and the newly added cellular call have the same priority for occupying the channel; when no idle cellular mobile channel exists in the cellular coverage area and the preemptible cellular channel in the dual coverage area of the cellular network and the wireless local area network needs to be preempted through competition, the preemption priority of the non-priority UVH call and the newly added cellular call is reduced to the priority level lower than that of the priority UVH call, namely, the priority UVH call has stronger channel preemption capability than the non-priority UVH call and the newly added cellular call;

c) decision algorithm for DVH (dynamic video H) and downlink vertical handover in heterogeneous network dual coverage area

The online voice call entering the double coverage area is processed differently according to the call type defined by the voice time threshold, and the priority voice call does not actively execute the DVH process unless other calls in the single cell coverage area apply for preemption; if no idle WLAN wireless channel exists, the non-priority voice call allowed to enter the dual coverage area still temporarily occupies the cellular mobile channel so as to avoid unnecessary on-line voice disconnection;

Based on the difference between the high bandwidth of the WLAN and the low bandwidth of the cellular network and the fact that a mobile terminal is generally provided with a super-large-capacity cache chip, the data transmission rate of a non-real-time online broadband data call in a heterogeneous network is increased to 2 times that of the non-real-time online broadband data call in a single cellular coverage area after the DVH process is completed; similarly, when the non-real-time online broadband data call in the heterogeneous network completes the UVH process, the data transmission rate is also reduced to half of the data transmission rate in the WLAN coverage area;

Total cell channel capacity in heterogeneous network ofBBasic bandwidth unit as long as the remaining idle channel capacity of the current cellThe service requirement of the channel application call is met, and the UVH call or the newly added cellular call can occupy the cellular mobile channel.