CN115002696B

CN115002696B - Time-limit-based non-real-time data variable-speed vertical switching method between heterogeneous networks

Info

Publication number: CN115002696B
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: 2023-08-01
Anticipated expiration: 2042-05-06
Also published as: CN115002696A

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-large capacity cache chip is commonly configured in a mobile terminal at present, comprehensively considers the difference between WLAN high bandwidth and cellular network low bandwidth, and provides a method for improving time-threshold-based priority jump vertical switching. The method reduces congestion level occupied by channels in a cellular coverage area by dynamically adjusting the transmission rate of non-real-time broadband data calls between heterogeneous networks. The invention has the advantages of obviously improving the system priority UVH call loss rate, the non-priority UVH call loss rate and the newly added cellular call blocking rate performance while maintaining the overall 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 between heterogeneous networks based on time limit.

Background

Currently, with the increasing demand of people for mobile access services, new generation wireless communication technologies are developing toward 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, whereas WLANs are characterized by small coverage and high bandwidth. And the interworking of the cellular mobile network and the WLAN can complement the advantages of the two and enhance the quality of service (QoS) of the provided service.

The process of switching connections between networks is called handover. Handoff between the same access technology networks (e.g., between WLANs) is referred to as horizontal handoff, while handoff between different access technology networks (e.g., cellular mobile network and WLAN) is referred to as vertical handoff. Vertical handoffs can be further divided into Downlink Vertical Handoffs (DVH) and Uplink Vertical Handoffs (UVH). For cellular mobile network and WLAN interworking systems, DVH refers to a vertical handoff from cellular mobile network to WLAN, and UVH refers to a vertical handoff from WLAN to cellular mobile network. DVH is a handover procedure for a mobile user from a low bandwidth large coverage to a high bandwidth limited coverage network, while UVH is a handover procedure for a mobile user from a high bandwidth limited coverage to a low bandwidth large coverage network.

Vertical handover between heterogeneous networks is an important challenge for the realization of seamless mobility for new generation mobile networks. In recent years, many handover methods for heterogeneous wireless network vertical handover have appeared, but these methods rarely involve vertical handover for channel preemption. In the paper A channel preemption model for vertical handoff in a WLAN-embedded cellular network published in journal Wireless Networks by t. shau et al 2010, a channel preemption vertical handover method (abbreviated as PMV method) suitable for interworking between a cellular mobile network and a WLAN is proposed, and the core idea is that: if the effective mobile channels in the cellular mobile network are all occupied, the new call only in the coverage area of the single cellular mobile network or the handover call which is switched to the coverage area of the single cellular mobile network by executing the UVH process discovers that the preemptive cellular mobile channels exist in the dual coverage areas of the cellular mobile network and the WLAN, and the channels can be preempted. The preempted on-line cellular call is forced to perform a DVH procedure with a down-link vertical handoff by 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 manner in which handover calls are handled will directly impact the quality of service (QoS) and performance of the interworking system providing services to mobile subscribers, i.katzela and m.naghshineh, as early as 1996, published paper "Channel Assignment Schemes for Cellular Mobile Telecommunication Systems: A Comprehensive Survey" in journal IEEE Personal Communications ", which states that: "the loss of a handover call should be avoided more in case of a blocking of a new call within the cellular mobile network". However, in the design of how to perform cellular mobile channel occupation and preemption for the new call only in the single cell coverage area and the vertical handover call performing UVH procedure to switch to the single cell coverage area, the PMV method does not consider the sequencing of the two, but gives UVH the right to compete and preempt the cellular mobile channel equally to the new call, so that the call loss rate performance of the UVH handover call cannot be further improved. Aiming at the deficiency of the PMV method, paper An Upward Priority Channel Preemption Scheme for Vertical Handoff in Cellular/WLAN Interworking proposes an uplink priority vertical switching method (UPPS method for short) applicable to a cellular mobile network and a WLAN interworking network on an international conference of IEEE WICOM in 2011. The method effectively improves UVH the loss rate performance of the handover call by increasing the priority of the UVH handover call in the uplink vertical handover with channel preemption, but thereby also increases the newly added cellular call blocking rate somewhat. For limited cellular mobile channel resources, UVH handover call loss rate and newly added cellular call blocking rate are contradictory two opposite sides, biasing either side, degrading the performance of the other. How to achieve the best balance between the two has been the focus of attention in the field of wireless communications. M. Salamah et al 2005 in journal "New Trends in Computer Networks" paper "A Fair Bandwidth Allocation Scheme for Multimedia Handoff Calls in Cellular Networks" states that: "for an online voice call, if the call duration is short, the call is dropped, the user will be very annoyed, and when the call duration is a certain time, the call is dropped, the user's dissatisfied emotion will not be as strong; also, for online data calls, a user may generally tolerate a drop in the connection time less than an acceptable range, but the dissatisfaction of that user will be quite intense when the drop occurs after the online data transmission has been in progress for a considerable period of time. Thus, M Salamah et al, in the above paper, propose a time-threshold channel allocation method (TTS method for short) for horizontal handover within a cellular network. The method classifies the priority of the on-line horizontal switching call according to different tolerations of the user to voice and data services by monitoring the on-line communication time of the horizontal switching call, and aims to improve the performance of the newly added call blocking rate while ensuring that the priority horizontal switching call of the time sensitive user has a lower loss rate. In IEEE WICOM'2012 international conference, paper A Time-threshold-based Upward Priority Scheme for Vertical Handoff in Cellular/WLAN Interworking applies the Time threshold strategy of M.Salamah et al for horizontal switching of the same network to the vertical switching among heterogeneous networks, and an uplink vertical switching method (TUPS method for short) based on the Time threshold among heterogeneous networks is provided. On the basis, an uplink priority jump vertical switching method (TPHS method for short) suitable for a cellular mobile network and a WLAN interworking network is proposed in paper A Time-threshold-based Priority Hopping Scheme for Vertical Handoff in Cellular/WLAN Interworking published in 2017 'IEEE Computer and Communications' International conference. The method provides a priority jump algorithm aiming at the occupation and preemption of the channels in the cellular coverage area on the basis of a vertical switching method based on a time threshold so as to adjust the capability of various calls competing for the cellular mobile channels in different environments, and simultaneously reduces the congestion degree of the channels in the cellular coverage area by designing a DVH decision algorithm of online voice calls in the dual coverage area. Nevertheless, how to further improve UVH call loss rate and newly added cellular call blocking rate performance remains an important goal of research. Because the mobile terminal is commonly configured with a super-large capacity cache chip at present, and meanwhile, the difference between the high bandwidth of the WLAN and the low bandwidth of the cellular network is considered, the transmission rate of the non-real-time online broadband data call in the heterogeneous network does not need to be completely the same 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 within the high bandwidth WLAN coverage area and buffered in a mobile terminal buffer chip. Therefore, the load pressure of a single cell coverage area in a heterogeneous network can be greatly reduced, the performance of the system UVH on the call loss rate and the newly added cell call blocking rate can be further improved, and the use efficiency of channels in the WLAN coverage area can be improved.

Disclosure of Invention

The invention aims to provide a non-real-time data variable-speed vertical switching method based on time limit among heterogeneous networks, which aims at overcoming the defects of the prior art. The method reduces congestion level occupied by channels in a cellular coverage area by dynamically adjusting the transmission rate of non-real-time broadband data calls between heterogeneous networks. The invention has the advantages of obviously improving the system priority UVH call loss rate, the non-priority UVH call loss rate and the newly added cellular call blocking rate performance while maintaining the overall high channel utilization rate of the system, and realizing the effective utilization of network channel resources.

The specific technical scheme for realizing the aim 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 between a cellular mobile network and a wireless local area network, the method comprises:

a) Online voice and broadband data call classification

Setting a voice and broadband data time threshold according to the call drop tolerance of a user by monitoring the online communication time of a call, wherein the voice time threshold is a time set value which is larger than the minimum call duration acceptable by the 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 tolerate the call drop by the broadband data user, so that the online voice and broadband data calls in a cellular coverage area are classified according to priority; an online voice call less than a voice time threshold and an online broadband data call greater than a broadband data time threshold are referred to as priority calls, while an online voice call greater than or equal to a voice time threshold and an online broadband data call less than or equal to a broadband data time threshold are referred to as non-priority calls;

b) Priority algorithm for occupying and preempting channels in heterogeneous network cellular coverage area

According to the priority of uplink vertical switching and the tolerance of a user to switching call disconnection, UVH with cellular mobile channel occupation and preemption requirements in heterogeneous network cellular coverage areas, namely uplink vertical switching call and newly added cellular call, a priority algorithm of the following channel occupation and preemption is designed: when there is an idle cellular mobile channel within the cellular coverage area, priority UVH calls, non-priority UVH calls and newly added cellular calls have the same priority of occupied channels; when no idle cellular mobile channel exists in the cellular coverage area, the preemption priority of the non-priority UVH call and the newly added cellular call is reduced to be lower than the priority of the priority UVH call by competing to preempt the preemptive cellular channel in the dual coverage area of the cellular network and the wireless local area network, namely, the priority UVH call has stronger preemption channel capacity compared with the non-priority UVH call and the newly added cellular call;

c) Heterogeneous network dual-coverage online voice call DVH decision algorithm

On-line voice calls entering the dual coverage area are processed differently according to the call types defined by the voice time threshold, and priority voice calls do not actively execute the DVH process unless other calls in the single cell coverage area are used for preempting the single cell coverage area; the call gives up the cellular mobile channel and occupies the WLAN wireless channel as long as the idle WLAN wireless channel exists, but if the idle WLAN wireless channel does not exist at the moment, the non-priority voice call which enters the dual coverage area is allowed to continue occupying the cellular mobile channel temporarily under the condition that no cellular mobile channel preemption occurs, so that unnecessary online voice disconnection is avoided;

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

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

e) Cellular mobile channel allocation within heterogeneous network cellular coverage area

The total capacity of the cell channels in the heterogeneous network isBThe UVH call or the newly added cellular call can occupy the cellular mobile channel as long as the remaining free channel capacity of the current cell can meet the traffic demand of the channel application call.

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

In an interworking system between cellular mobile networks and wireless local area networks, an on-line broadband data call entering a dual coverage area should perform as much as possible the DVH procedure, i.e. the call drops the cellular mobile channel as long as there is an idle WLAN radio channel present, instead occupying the WLAN radio channel. However, if no idle WLAN radio channel is present at this time, the on-line broadband data call entering the dual coverage area is allowed to continue to occupy the cellular mobile channel temporarily without cellular mobile channel preemption occurring, so as not to add unnecessary on-line broadband data drops.

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

Drawings

Fig. 1 is a block diagram of an interworking system of a cellular mobile network and a wireless local area network;

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

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

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

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

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

Detailed Description

The invention is further described in detail below with reference to the drawings and examples. The following examples are not intended to limit the invention. Variations and advantages that would occur to one skilled in the art are included in 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 area 1, vertical handover 2, and dual coverage area 3; the architecture provides voice and broadband data services for cellular mobile terminals and wireless terminals within the coverage area of the WLAN. Channel capacity of each cell in example simulationBFor 20BBUs (basic bandwidth units), each WLAN coverage channel capacity is 54 BBUs. To meet the service QoS requirements, a single voice call needs to occupy one basic bandwidth unit channel, a single real-time wideband data call and each non-real-time wideband data call in a single cellular coverage area need to occupy two basic bandwidth unit channels, and each non-real-time wideband data call in a WLAN coverage area needs to occupy four basic bandwidth unit channels. The process of generating new calls in a cell follows the Poisson process with mean value of lambdac, while the process of generating new calls in the coverage area of a WLAN follows the Poisson process with mean value of lambdaw (where lambdaw takes 0.04 call/s), and the call blocking rate and loss rate performance indexes involved in the invention are mainly affected by the change of lambdac. The communication duration of each call obeys a negative exponential distribution with an average of 6 minutes. The residence time of the online calling user within the single cell and single WLAN coverage areas obey a negative exponential distribution with an average of 2 minutes and 4 minutes, respectively. The voice and broadband data time thresholds for prioritizing and non-prioritizing UVH calls are 120 seconds and 30 seconds, respectively.

Fig. 2, 3 and 4 show simulated graphs of priority UVH call loss rate, non-priority UVH call loss rate and newly added cellular call blocking rate versus cellular load, respectively. In fig. 2: the abscissa is the cellular call arrival rate; the ordinate is 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 B is TPHS. From the simulation results, it can be seen that: compared with a TPHS method, the non-real-time broadband data variable transmission priority vertical switching method based on the time threshold among heterogeneous networks obviously improves the performance of the system priority UVH call loss rate, the non-priority UVH call loss rate and the newly-added cellular call blocking rate. This is because the data transmission rate of the non-real-time broadband data call in the system is doubled after entering the WLAN coverage area through the DVH process, so that the information transmission quantity of the non-real-time broadband data call can be completed in the WLAN coverage area as much as possible, thereby greatly reducing the crowding degree of the cellular mobile channels in the single-cell coverage area under the heavy load condition; meanwhile, when the non-real-time broadband data call returns to the single cell coverage area through the UVH process, the algorithm designed by the method 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 can ensure that the variable speed transmission of the non-real-time broadband data call does not burden the load of the single cell coverage area. As can be seen from fig. 2: when the average arrival rate lambdac of the newly added call of the cell reaches 0.08call/s with heavier load, the priority UVH call loss rates of the method and the TPHS method are respectively 0 and 7.20E-3, and the improvement degree of the method for the priority UVH call loss rate reaches 100% relative to the TPHS method; also, in FIG. 3, when λc reaches 0.07call/s, the non-priority UVH call loss rates of the inventive method and TPHS method are 1.08E-2 and 2.90E-2, respectively, and the improvement of the non-priority UVH call loss rate by the inventive method over the TPHS method is 62.76%; again, it can be further seen from fig. 4 that: when the average arrival rate lambdac of the new cell call is also 0.07call/s, the blocking rate of the new cell call of the method and the TPHS method of the invention is respectively 1.75E-2 and 5.80E-2, and the improvement degree of the method of the invention on the blocking rate of the new cell call reaches 69.83 percent relative to the TPHS method, and the improvement effect is quite obvious. Fig. 5 and 6 show simulated graphs of cellular mobile channel utilization and WLAN radio channel utilization versus cellular loading. 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 WLAN wireless channel utilization; curve a is the invention and B is TPHS. Although fig. 5 shows that the inventive method has reduced cellular mobile channel utilization compared to the TPHS method, this is the only design objective of the inventive method. The method greatly reduces the pressure of cellular mobile channel allocation of the cellular coverage area, and can accommodate more online voice calls and real-time broadband data calls in the single cellular coverage area; fig. 6 shows that the method of the present invention significantly improves the WLAN radio channel utilization compared to the TPHS method. Therefore, overall channel utilization of the system is not reduced as a whole, but only part of the transfer from the cellular mobile network to the WLAN network is performed, i.e. the WLAN network shares part of the load of the cellular mobile network.

Thus, by the figures and examples analysis, it is demonstrated that: the non-real-time data variable-speed vertical switching method based on the time limit provided by the invention obviously improves the performance of the system priority UVH call loss rate, the non-priority UVH call loss rate and the newly added cellular call blocking rate while maintaining the utilization rate of the whole channel of the system, and realizes the beneficial effect of effectively utilizing the channel resources.

Claims

1. The non-real-time data variable speed vertical switching method based on time limit between heterogeneous networks is characterized in that the method comprises the following steps:

a) Online voice and broadband data call classification

c) Heterogeneous network dual-coverage-area online voice call DVH (digital video broadcasting) downlink vertical switching decision algorithm