It defines the multiframe structure as well. The six extra padding frames can be lumped together into an extended direct mode frame or they can be evenly distributed within a multiframe so that each pad exists in every three direct mode frames, as shown in Fig. The two blocks for modulated data bits, BKN 1 and BKN2, for said synchronization burst is emulated within the same symbol, symbol 1. The frames of broadband signals are arranged as time slots to form a direct mode multiframe. To form 18 direct mode frames within a multiframe, each direct mode frame will require 11 WiMAX Jrames. Normal burst and synchronization burst contain two independent fields containing modulation bits of the same type. The third burst, normal burst, is used to carry traffic data.
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The present invention relates generally to network communications, more particularly to digital network communications. Two time slots are provided for a call transaction, a first and third time slot within a direct mode frame, for every communication channel.
Alternatively, to avoid using padding frames, a fixed number of WiMAX frames can be allocated for each direct mode frame. Part of one specific frame of broadband signals within a duration exactly or close to that of a TETRA direct mode frame is used to emulate a time slot.
A mimls skilled in the art should be able to apply the discussion on mapping with any given number of WiMAX frames per direct mode frame, with or without padding frames. A proper modulation is later assigned for each direct mode burst including synchronization burst and normal burst, and optionally, linearization burst. Consequently, the mobile terminal can be used as a private cordless phone.
In WiMAX, three carrier sets are used to carry preamble. More transparent zones or one teetra transparent zone can be accommodated for more direct mode channels to enable more concurrent calls. The preamble will be used by slave mobile station to synchronize with the transmitting mobile station. When a base station is operating, the base station provides an extra zone, called transparent zone, within its frames. The emulation of direct-mode synchronization burst requires the use of a preamble which occupies symbol 0 of the transparent zone.
The control bits may be used, for example, to indicate whether one or two logical channels are mapped to the two blocks of modulated data bits. A system for enabling a mobile station MS to communicate directly with another 5 mobile station using complete, subset or superset of TETRA direct mode-like features and at the same time to be compatible with the tetea wireless broadband network air interface, said system comprising: The preamble of direct mode burst shall be different from the one used for WiMAX.
The burst formats of these two channels are defined according to frequency correction and synchronization channel burst formats used in the cellular mobile network.
Other than these two channels, there are linearization channel, signaling channel and stealing channel. In the discussion that follows, twelve WiMAX frame per direct mode frame is chosen to achieve 1.
Alternatively, some bandwidth request protocol to the base station may be defined so that a mobile station that wants to make getra direct mode call may be allocated one or more direct mode channels. This is akin to frequency efficient mode of operation in TETRA direct mode where it supports up to two concurrent calls.
The invention will now be described in greater detail, by way of an example, with reference to the accompanying drawings, in which:. A call can occur in direct mode first channel, Channel A using a first and third time slot at time slot 1 and 3, while another call occurs in direct mode second channel, Channel B using a second and fourth time slot at time slot 2 and 4.
A transmitting direct mode mobile station will use all the subcarriers for transmission.
If ten WiMAX frame is used per direct mode frame, the multiframe will have a duration of milliseconds. A direct mode physical channel comes into existence when a call is active. The method of claim 1wherein one or more time slot is allocated to one or more transparent zones in a target wireless broadband network frame.
For emulating TETRA direct mode normal burst, to simplify allocation of transparent zone for direct mode operation, the number of OFDMA symbols used is set to two, which is the same number of symbols allocated for mims burst.
It needs a base station to broadcast data. There are three different kinds of burst, as shown in Fig.
Frames of broadband signals are arranged as a time slot to form a direct mode multiframe, said multiframe is made up of 18 direct mode frames according to TETRA direct mode specification. Direct mode tetga communication to tetda made when network coverage is not available and allows one of the TETRA terminals to act as relays for a signal. A system for enabling a mobile station MS to communicate directly with another 5 mobile station using complete, subset or superset of TETRA direct mode-like features and at the same time to be compatible with the target wireless broadband network air interface, said system comprising:.
TETRA direct tetar normal burst makes use of two preambles, a first and second preamble. The pilot carriers in the FUSC slots used in the two symbols may be used for channel tracking until another synchronization burst arrives. The transmitting mobile station is the master while a receiving mobile station is the slave. The method tetraa claim 1wherein said step of mapping TETRA direct mode multiframe structure is performed, by mapping a number of wireless broadband network frames such that the TETRA direct mode multiframe duration of 1.