Nhiều giao thức truy cập đối với truyền thông di động P9

... stack-based algorithms have the disadvantage of requiring immediate (although normally only binary) acknowledgements to work properly, which, as discussed at length earlier, is difficult to achieve in ... simulation study for different mixtures of voice and data traffic is conducted, where the latter consists either of Web traffic, email traffic, or a combination of the two. Preceding the discussion of ... Semi-proportional Priority Distribution In 1996/1997, Celia Fresco Diez, an exchange student at King’s College London, continued our earlier investigations on the GPRS random access. Some of her findings are summarised...

Nhiều giao thức truy cập đối với truyền thông di động P1

... usually distinguished. These are the pathloss, slow fading or shadowing, and fast fading or multi- path fading. The pathloss describes the average signal attenuation as a function of the distance ... GPRS, discrimination between the access delay performance experienced by different services is possible through computation of different permission probabilities for contending terminals according ... session. The multiple access capability derives from the use of different spreading codes for individual users. Because of the spreading of the spectrum, CDMA systems are also referred to as spread...

Nhiều giao thức truy cập đối với truyền thông di động P2

... standardisation of the UTRA FDD and TDD modes from ETSI (with UTRA now standing for universal terrestrial radio access rather than UMTS terrestrial radio access). Apart from ETSI and Japanese bodies, ... co-ordination is a different matter; a GSM- based cordless telephony system is a part of the GSM evolution story. As far as efﬁcient use of the radio spectrum is concerned, refer to the discussion ... was not possible, an attempt would be made to merge different proposals into a single one in a consensus building phase. While all bodies standardising such systems actually submitted their proposals...

Nhiều giao thức truy cập đối với truyền thông di động P3

... can readily be split into the sub-problems of: (a) providing a basic multiple access scheme such as frequency-division multiple access (FDMA), time-division multiple access (TDMA) or code-division ... layer, as indicated in Figure 3.1. In a mobile communications system, however, the transmission medium is the error prone radio channel, a medium subject to shadowing and fast fading. Designing ... 3.2 Multiple access protocol classiﬁcation according to Rom and Sidi access protocol’. Interestingly, for our purposes, time-division and frequency-division multiplexing are treated in Reference...

Nhiều giao thức truy cập đối với truyền thông di động P4

... symbols, each symbol corresponding to a two-way transmission distance of approximately 1100 m. The maximum two-way transmission distance is 70 km, hence the maximum cell radius 35 km. Accounting for ... frequency hopping is a different matter, as discussed in more detail in Subsection 4.6.5. According to Reference [105], the main advantages of this feature are two-fold. Firstly, diversity on one transmission ... channel ﬂuctuations, the time diversity obtained through interleaving and error coding is typically sufﬁcient. For slow moving mobiles, on the other hand, a fading dip may extend over more than...

Nhiều giao thức truy cập đối với truyền thông di động P5

... expanding on a paper from 1976 [244], he provided expressions for the variance in direct-sequence CDMA (DS/CDMA) systems, with random coding and BPSK modulation, as a function of the spreading ... Coding in CDMA According to Lee, coding is always beneﬁcial and sometimes crucial in CDMA applica- tions [6]. Results reported in References [137,247,250,251] conﬁrm this statement 7 . In digital ... reasonable accuracy by a set of formulae readily available from literature, preferably parameterised in a manner that permits different operating conditions to be investigated easily. MAC layer...

Nhiều giao thức truy cập đối với truyền thông di động P6

... possible. 6.2.3.2 Differences in the Random-Coding Case There are subtle differences in the contention procedure for the ‘pure’ random-coding case. Since no code-slots are discriminated, the ... contention mode between individual cycles. 6.3 MD PRMA with Time-Division Duplexing 6.3.1 Approaches to Time-Division Duplexing There are two fundamental approaches to providing time-division duplexing ... protocol suitable for frequency-division duplexing is described. Then, the implications of different approaches to time-division duplexing on the protocol operation will be discussed. Finally, the two...

Nhiều giao thức truy cập đối với truyền thông di động P7

... Poisson distributed, this distribution will be used in the following. If we ignore the fact that a continuous distribution is being compared with a discrete distribution, when K  0, the Poisson distribution ... steady-state distribution (Equation (7.2)) is a binomial distribution with parame- ters M and α v . The Poisson distribution with mean V = M · α v is a good approximation of the binomial distribution, ... < 0.05 and M>10). The ﬁrst condition must hold for the variance of the binomial distribution, M · α v · (1 − α v ), to match roughly that of the Poisson distribution, V . Here, α v is signif-...

Nhiều giao thức truy cập đối với truyền thông di động P8

... (assuming immediate acknowledgement); • the added traffic in the case of interleaving (I/L) due to dedicated request bursts and on average two additional bursts per voice spurt due to rounding up the ... performance of this protocol are discussed in Reference [37]. 2 This problem did not arise in Chapter 7, since a terminal, while holding a reservation in a certain time-slot, did not reserve a specific ... not immediate), the Bayesian algorithm needs to be modified, that is, p v needs to be calculated through Equation (6.7). Unlike the acknowledgements, p v is assumed to be broadcast immediately...

Tài liệu Nhiều giao thức truy cập đối với truyền thông di động P10 doc

... categorised as either dedicated or common physical channels.10.2.2.1 Dedicated Physical ChannelsAll dedicated physical channels feature a radio frame length of 10 ms, with each framesubdivided into 15 ... acquisition Indicators (API) responding to CPCH access preambles.• The CPCH Collision Detection/Channel Assignment Indicator CHannel (CD/CA-ICH)carrying either Collision Detection Indicators (CDI), ... indicator channel (AICH)Access preamble acquisition indicator channel (AP-AICH)Paging indicator channel (PICH)CPCH status indicator channel (CSICH)Collision-detection/channel-assignment indicatorChannel...

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