Translation lte/lte-advanced for Mobile Broadband-10.4

Source: Internet
Author: User

10.4 downlink L1/L2 Control signaling

The transmission of the uplink and downlink channels requires a specific "downstream control signaling" to provide support. The downlink control signaling is often referred to as the "downlink l1/l2 Control Signaling", which means that the control signaling is partly from the physical layer (L1) and partly from the MAC layer (L2). The following downlink control signaling details include:

1. downlink dispatch allocation, this information tells the terminal how to correctly receive, demodulation and decoding the Dl-sch (downlink shared channel) information;

2. Uplink dispatching authorization, which tells the terminal to transmit uplink data using the wireless resources and transmission format;

3. HARQ feedback, this information tells the terminal through Ul-sch uploaded data is successfully received;

4. TPC, Power Control command, tell the terminal how to adjust the transmission uplink data;

5. Other special purpose information, such as MBSFN notification.

As shown in 10.20, the downlink L1/L2 control signaling is transmitted at the beginning of each sub-frame. Each sub-frame can be considered to consist of a control domain and a data field, and the downstream L1/L2 control signaling belongs to the control domain. To simplify the design complexity, the control domain consists of an integer number of characters, usually 1, 2, or 3 OFDM characters (for narrower cell bandwidth, such as a bandwidth consisting of 10 or fewer resource blocks, the control area requires 2, 3, or 4 OFDM characters to satisfy the transmission of the information). When using carrier aggregation, each carrier has a control domain.

The size of the control domain can be represented by the number of OFDM characters. The size of the control domain can be configured independently on each sub-frame of each carrier (translator Note: In the case of carrier aggregation), which can be dynamically adjusted according to the current transmission situation. When you need to control the user compared to the hour, you can reduce the size of the control domain, more resources to the transfer of data.

The reason that the control domain is placed at the beginning of the sub-frame is to allow the terminal to decode the downlink dispatch information at an early stage (the translator note: The terminal can know how to decode the Dl-sch information), so that the terminal before the end of the sub-frame transmission can be Dl-sch demodulation and decoding, reduce dl-sch decoding delay, This reduces the delay of the overall downstream transmission. More importantly, the control domain is placed at the beginning of the sub-frame, then those non-scheduled terminals do not need to demodulation, decoding Dl-sch data, reducing their power consumption.

The downlink l1/l2 control signaling contains the following four types of physical channels:

    • The physical control format indicates the channel (Pcfich), which tells the size of the control domain of the terminal, and there is only one pcfich in each carrier;
    • Physical downlink control channel (PDCCH), including downlink Dispatch and uplink dispatching authorization information, each PDCCH carrying one or a set of terminal information;
    • Physical Mixed Arq channel (PHICH), carrying Harq feedback information;
    • Relays the physical downlink control channel (R-PDCCH), which is used when relaying.

As mentioned above, the size of the control domain is up to 3 (4 in narrow bandwidth). However, with some exceptions, the control domain for sub-frame 1 and sub-frame 6 in TDD mode does not exceed 2 characters, because the sync signal in TDD mode occupies the 3rd character. Similar to the MBSFB sub-frame, the control domain is also limited to a limit of 2 characters.

Translation lte/lte-advanced for Mobile Broadband-10.4

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