| 摘要 |
A method to determine an access frequency band in a communication access network. The communication access network includes terminals (T11, T12, T13, ..., T31, ...) and a head-end (HE) which includes transceivers (TRX1, TRX2, TRX3, ...). The head-end is downstream coupled to each one of the terminals via a downstream common link (Lc) and a tree-like distributive network . Each one of the transceivers provides to a combiner (COMB) included in the head-end a downstream signal (Sd1, Sd2, Sd3, ...) in a frequency band associated by means of a predetermined first association to one of the transceivers. The downstream signals are together combined by the combiner into a downstream modulated signal (S-MOD). The downstream modulated signal is broadcasted from the head-end to the terminals. A first one (T12) of the terminals is upstream coupled to at least one receiving transceiver (TRXrec1 , TRXrec2, ... ) which is one of the transceivers, via a common upstream link and at least one upstream sublink. The access frequency band is one of the frequency bands (CH1, CH2, CH3, ...) to be used by the first terminal (T12) to filter out of the downstream modulated signal one of the downstream signals provided by an access transceiver which is one of the transceivers in order to establish a communication between the access transceiver and the first terminal. The method includes the steps of: a) choosing by the first terminal out of the frequency bands a start frequency band (CHst); and b) determining by the first terminal with the start frequency band and according to a predetermined second association an upstream frequency band (CHu). The upstream frequency band is one of the upstream frequency bands whereof each one is associated by means of the predetermined second association to one of the frequency bands; and c) transmitting by the first terminal within the upstream frequency band an access request signal (AR(T12)) to the receiving transceivers; and d) filtering by the receiving transceivers out of incoming signals which includes the access request signal within a predetermined upstream frequency bands according to the predetermined first association and the predetermined second association and thereby providing a filtered signal; and e) in the event that the upstream frequency band substantially equals to one of the upstream frequency bands used by a first (TRXrec1) receiving transceiver in the step d) whereby the filtered signal substantially equals to t he access request signal, confirming to the first terminal by the head-end (HE) tha t the start frequency band constitutes the access frequency band; f) in the event that after a predetermined time from sending the access request signal without receiving of the confirmation of the step e), repeating t he steps of the method with another start frequency band (CHst').
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