Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655466
S. Kato
Personal communications systems (PCS) provide the capability to communicate anywhere, anytime with anybody by featuring personal, person-based, and personalized services to serve different customers' different requests. This concept, communications with, everyone, at anywhere and anytime is the ultimate goal of communications and translates to portability of services. The portability of handset has been improved very much during the last several years and now what required is enhancement of portability of multimedia services with which everybody can enjoy not only voice transmission but also email/text transmission services. A number of PCS have been working toward this direction and true multimedia communications will be realized through wireless communications systems first.
{"title":"Wireless personal and multimedia communications","authors":"S. Kato","doi":"10.1109/ICPWC.1997.655466","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655466","url":null,"abstract":"Personal communications systems (PCS) provide the capability to communicate anywhere, anytime with anybody by featuring personal, person-based, and personalized services to serve different customers' different requests. This concept, communications with, everyone, at anywhere and anytime is the ultimate goal of communications and translates to portability of services. The portability of handset has been improved very much during the last several years and now what required is enhancement of portability of multimedia services with which everybody can enjoy not only voice transmission but also email/text transmission services. A number of PCS have been working toward this direction and true multimedia communications will be realized through wireless communications systems first.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124422625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655469
Yan Jiang, V. Bhargava
Personal communications systems (PCS) represent a rapidly growing and increasingly important segment of the telecommunication industry. We investigate the issue of mobility-oriented guard channel assignment in a mixed traffic load environment. According to different generation sources, calls are first distinguished between handoff and original calls. The original calls are further divided into four classes based on their different mobility and load characteristics, i.e., high load/high mobility; low load/high mobility; high load/low mobility; low load/low mobility. In order to reduce the forced termination of handoff calls, the priority is given to high mobility calls over low mobility calls, and with the same mobility level, high load calls are assumed to have the priority over low load calls. We compare the forced termination and uncompleted call probabilities when assigning different sets of guard channels to the handoff and prioritized original calls. The analytical model presented can effectively cover a wide range of mobility and load levels.
{"title":"Mobility-oriented guard channel assignment for personal communication systems","authors":"Yan Jiang, V. Bhargava","doi":"10.1109/ICPWC.1997.655469","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655469","url":null,"abstract":"Personal communications systems (PCS) represent a rapidly growing and increasingly important segment of the telecommunication industry. We investigate the issue of mobility-oriented guard channel assignment in a mixed traffic load environment. According to different generation sources, calls are first distinguished between handoff and original calls. The original calls are further divided into four classes based on their different mobility and load characteristics, i.e., high load/high mobility; low load/high mobility; high load/low mobility; low load/low mobility. In order to reduce the forced termination of handoff calls, the priority is given to high mobility calls over low mobility calls, and with the same mobility level, high load calls are assumed to have the priority over low load calls. We compare the forced termination and uncompleted call probabilities when assigning different sets of guard channels to the handoff and prioritized original calls. The analytical model presented can effectively cover a wide range of mobility and load levels.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125216771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655556
G. Karetsos, C.C. Kossidas, E. Protonotarios
We study and compare TDMA, CDMA and ALOHA as well as hybrid TDMA/CDMA, ALOHA/CDMA and ALOHA/TDMA as possible candidates for the MAC protocol of the return channel in a cellular interactive TV architecture. A comparative analysis of the access characteristics between the previously mentioned MAC methods is provided on the basis of the number of users and the traffic rate involved. The nature of the multiple access techniques examined, especially for the hybrid ones, does not allow for making objective performance comparisons but rather simple and approximate ones. The advantages and disadvantages of each method are reviewed and implementation guidelines are provided for the most feasible solutions.
{"title":"Evaluation of multiple access methods for the MAC protocol of the return channel in a cellular interactive TV architecture","authors":"G. Karetsos, C.C. Kossidas, E. Protonotarios","doi":"10.1109/ICPWC.1997.655556","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655556","url":null,"abstract":"We study and compare TDMA, CDMA and ALOHA as well as hybrid TDMA/CDMA, ALOHA/CDMA and ALOHA/TDMA as possible candidates for the MAC protocol of the return channel in a cellular interactive TV architecture. A comparative analysis of the access characteristics between the previously mentioned MAC methods is provided on the basis of the number of users and the traffic rate involved. The nature of the multiple access techniques examined, especially for the hybrid ones, does not allow for making objective performance comparisons but rather simple and approximate ones. The advantages and disadvantages of each method are reviewed and implementation guidelines are provided for the most feasible solutions.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123421063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655561
F. Barceló, A. Ramon
The packet reservation multiple access (PRMA) protocol has been proposed as a candidate for the third generation of mobile radio systems to obtain a statistical multiplexing gain from the bursty character of speech, probably the main service to be provided by a mobile network. The PRMA is derived from the slotted Aloha protocol, and being a reservation protocol makes it suitable to cope with the quality needs of the voice service. In the technical literature it is not difficult to find papers which deal with the performance evaluation of systems which use the PRMA; the mathematical tool known as equilibrium point analysis (EPA) is used in most of this work to calculate the performance of the system. The results of the EPA are cumbersome to compute and require programming complex mathematical expressions. Instead of this method, a model based on queueing theory is proposed to evaluate the PRMA protocol. The probability of packets being dropped and talkspurts being clipped are easily computed according to the proposed approach.
{"title":"PRMA performance evaluation based on queueing theory","authors":"F. Barceló, A. Ramon","doi":"10.1109/ICPWC.1997.655561","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655561","url":null,"abstract":"The packet reservation multiple access (PRMA) protocol has been proposed as a candidate for the third generation of mobile radio systems to obtain a statistical multiplexing gain from the bursty character of speech, probably the main service to be provided by a mobile network. The PRMA is derived from the slotted Aloha protocol, and being a reservation protocol makes it suitable to cope with the quality needs of the voice service. In the technical literature it is not difficult to find papers which deal with the performance evaluation of systems which use the PRMA; the mathematical tool known as equilibrium point analysis (EPA) is used in most of this work to calculate the performance of the system. The results of the EPA are cumbersome to compute and require programming complex mathematical expressions. Instead of this method, a model based on queueing theory is proposed to evaluate the PRMA protocol. The probability of packets being dropped and talkspurts being clipped are easily computed according to the proposed approach.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123595027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655500
A. Prasad, K. Seki
This paper presents and analyses the performance of a novel channel sharing protocol. The protocol uses the p-persistence algorithm to access the channel and a token for fair channel sharing. Token passing is controlled by a base station (BS). A user, PS, can join a channel if the channel is idle. Channel idle information is given by an idle token from the BS. Numerical results of the protocol are given in terms of load, G and throughput, S. Numerical results are also compared with that of carrier sense multiple access protocol with collision avoidance (CSMA/CA). Results show that the proposed scheme outperforms CSMA/CA when the number of channels are three or more.
{"title":"Capacity enhancement of indoor wireless communication system with a novel channel sharing protocol","authors":"A. Prasad, K. Seki","doi":"10.1109/ICPWC.1997.655500","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655500","url":null,"abstract":"This paper presents and analyses the performance of a novel channel sharing protocol. The protocol uses the p-persistence algorithm to access the channel and a token for fair channel sharing. Token passing is controlled by a base station (BS). A user, PS, can join a channel if the channel is idle. Channel idle information is given by an idle token from the BS. Numerical results of the protocol are given in terms of load, G and throughput, S. Numerical results are also compared with that of carrier sense multiple access protocol with collision avoidance (CSMA/CA). Results show that the proposed scheme outperforms CSMA/CA when the number of channels are three or more.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125311654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655559
A. Hottinen, R. Wichman, P. Soininen
We study the throughput of ALOHA based packet radio employing code division multiple access. In particular, we quantify the throughput increase achievable by linear multiuser detection and iterative multistage detection. In the context of ALOHA, multiuser detection is seen as a viable error recovery mechanism, which results in considerably smaller retransmission probabilities, and subsequently, higher throughput. The analysis suggests significant increase in throughput when compared to ALOHA operated in conjunction with a conventional CDMA receiver.
{"title":"On the throughput of ALOHA in the presence of multiuser detection","authors":"A. Hottinen, R. Wichman, P. Soininen","doi":"10.1109/ICPWC.1997.655559","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655559","url":null,"abstract":"We study the throughput of ALOHA based packet radio employing code division multiple access. In particular, we quantify the throughput increase achievable by linear multiuser detection and iterative multistage detection. In the context of ALOHA, multiuser detection is seen as a viable error recovery mechanism, which results in considerably smaller retransmission probabilities, and subsequently, higher throughput. The analysis suggests significant increase in throughput when compared to ALOHA operated in conjunction with a conventional CDMA receiver.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121911772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655487
S. Kishore, P. Agrawal, K. Sivalingam, Jyh-cheng Chen
Mobile multimedia systems must-amongst other things-account for user mobility in its network architecture. We present strategies for accommodating continuous service to mobile users via modifications in the design of the multiple access (MAC) protocol. More specifically, we focus on the adjustments required in the scheduling mechanism operating at base stations which grants access to mobile terminals by assigning them channels and time slots. In order to meet the needs to such mobile users, we propose a scheduler that uses anticipatory handoff indications from neighboring base stations to pre-assign slots for mobiles that are close to entering its coverage area. The paper examines the considerations necessary in pin-pointing such potential handoff mobiles. Additionally, an alternate MAC frame structure is presented to accommodate these potential users. Parameters that improve the reliability and utilization of these assignments are also studied.
{"title":"MAC layer scheduling strategies during handoff for wireless mobile multimedia networks","authors":"S. Kishore, P. Agrawal, K. Sivalingam, Jyh-cheng Chen","doi":"10.1109/ICPWC.1997.655487","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655487","url":null,"abstract":"Mobile multimedia systems must-amongst other things-account for user mobility in its network architecture. We present strategies for accommodating continuous service to mobile users via modifications in the design of the multiple access (MAC) protocol. More specifically, we focus on the adjustments required in the scheduling mechanism operating at base stations which grants access to mobile terminals by assigning them channels and time slots. In order to meet the needs to such mobile users, we propose a scheduler that uses anticipatory handoff indications from neighboring base stations to pre-assign slots for mobiles that are close to entering its coverage area. The paper examines the considerations necessary in pin-pointing such potential handoff mobiles. Additionally, an alternate MAC frame structure is presented to accommodate these potential users. Parameters that improve the reliability and utilization of these assignments are also studied.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123390664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655555
R. Ganesh, V. O'Byrne
The capacity of both AMPS and CDMA have been the issue of countless papers in the open literature. However, little emphasis has been given to how one may migrate from analog to CDMA, and how the underlying analog system is impacted by the sharing of the spectrum between the two technologies. Such practical issues may reduce the realized capacity below the sum of the theoretical capacity of the individual systems. In an overlay system the objective is to increase the capacity of the total deployed system rather than that of the digital system, or analog system alone. This paper discusses some preliminary results and focuses on such issues as using the coverage advantage of CDMA over analog to decrease the required number of cell sites that require conversion to dual-mode, and how this affects the underlying analog system and the effective capacity of the total system. As more demands occur on the system, the question arises as to whether one should deploy CDMA in more analog cells in the dual-mode footprint, or opt for an additional carrier in either a portion or in the total footprint. The various options available to the network provider are analyzed with the objective of optimization of the total system capacity.
{"title":"Improving system capacity of a dual-mode CDMA network","authors":"R. Ganesh, V. O'Byrne","doi":"10.1109/ICPWC.1997.655555","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655555","url":null,"abstract":"The capacity of both AMPS and CDMA have been the issue of countless papers in the open literature. However, little emphasis has been given to how one may migrate from analog to CDMA, and how the underlying analog system is impacted by the sharing of the spectrum between the two technologies. Such practical issues may reduce the realized capacity below the sum of the theoretical capacity of the individual systems. In an overlay system the objective is to increase the capacity of the total deployed system rather than that of the digital system, or analog system alone. This paper discusses some preliminary results and focuses on such issues as using the coverage advantage of CDMA over analog to decrease the required number of cell sites that require conversion to dual-mode, and how this affects the underlying analog system and the effective capacity of the total system. As more demands occur on the system, the question arises as to whether one should deploy CDMA in more analog cells in the dual-mode footprint, or opt for an additional carrier in either a portion or in the total footprint. The various options available to the network provider are analyzed with the objective of optimization of the total system capacity.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121457948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655538
K. Fall, P. Agrawal, K. Sivalingam
The goal of mobile computing is to provide seamless connectivity to resources in a backbone wired network. It should make computing facilities at wireless end points, such as laptops, PDAs, and other hand held devices, comparable to their wire-line counterparts. The limited bandwidth and error prone nature of the wireless channel present many challenges to achieving this goal. Properly architected network interfaces can overcome some of the challenges. This paper examines system architectures of network interfaces used in several research test beds and commercial mobile computing systems. In particular, the paper examines the interface architectures of systems including Bell Labs's SWAN system, Xerox PARCTAB, Berkeley's Infopad, and Lucent's WaveLAN.
{"title":"Survey of wireless network interfaces for mobile computing devices","authors":"K. Fall, P. Agrawal, K. Sivalingam","doi":"10.1109/ICPWC.1997.655538","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655538","url":null,"abstract":"The goal of mobile computing is to provide seamless connectivity to resources in a backbone wired network. It should make computing facilities at wireless end points, such as laptops, PDAs, and other hand held devices, comparable to their wire-line counterparts. The limited bandwidth and error prone nature of the wireless channel present many challenges to achieving this goal. Properly architected network interfaces can overcome some of the challenges. This paper examines system architectures of network interfaces used in several research test beds and commercial mobile computing systems. In particular, the paper examines the interface architectures of systems including Bell Labs's SWAN system, Xerox PARCTAB, Berkeley's Infopad, and Lucent's WaveLAN.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131764499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-12-17DOI: 10.1109/ICPWC.1997.655554
P.A. Leppanen, P. Pirinen
A method combining TDMA and CDMA in a digital cellular system is presented. This method makes use of complementary code sets. These codes have been selected due to their ideal autocorrelation and noninteracting characteristics. With these code sets orthogonality between users can be maintained even in the fading multipath channel which is a valuable property that cannot be provided with conventional multiple access codes. Bit error rate simulations have been made to test the link level performance of the system. Both AWGN and Rayleigh fading channels have been employed. Simulation results confirmed that complementary code sets are well adapted for use as multiple access codes in a mobile radio environment. Link level simulations pointed out that by using complementary code sets the number of non-interacting users in the Rayleigh fading channel on a single carrier can be increased. One clear advantage compared to the traditional CDMA systems is that power control is not necessary within a cell. Neither are the time synchronization requirements so strict as usual. The Erlang radio capacity was studied. The results indicated that approximately a twofold improvement over TDMA is possible with hybrid techniques.
{"title":"A hybrid TDMA/CDMA mobile cellular system using complementary code sets as multiple access codes","authors":"P.A. Leppanen, P. Pirinen","doi":"10.1109/ICPWC.1997.655554","DOIUrl":"https://doi.org/10.1109/ICPWC.1997.655554","url":null,"abstract":"A method combining TDMA and CDMA in a digital cellular system is presented. This method makes use of complementary code sets. These codes have been selected due to their ideal autocorrelation and noninteracting characteristics. With these code sets orthogonality between users can be maintained even in the fading multipath channel which is a valuable property that cannot be provided with conventional multiple access codes. Bit error rate simulations have been made to test the link level performance of the system. Both AWGN and Rayleigh fading channels have been employed. Simulation results confirmed that complementary code sets are well adapted for use as multiple access codes in a mobile radio environment. Link level simulations pointed out that by using complementary code sets the number of non-interacting users in the Rayleigh fading channel on a single carrier can be increased. One clear advantage compared to the traditional CDMA systems is that power control is not necessary within a cell. Neither are the time synchronization requirements so strict as usual. The Erlang radio capacity was studied. The results indicated that approximately a twofold improvement over TDMA is possible with hybrid techniques.","PeriodicalId":166667,"journal":{"name":"1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114781236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：