Though RLC (Radio Link Control) layer in LTE is similar to that of UMTS, but still there are some significant differences. One of the big change is RLC LTE header structure for different PDU (Protocol Data Unit) types.
When it comes to LTE, RLC can have the following PDU types
- RLC TMD PDU
- RLC UMD PDU
- RLC AMD PDU
- RLC AMD PDU Segment
- RLC Status PDU
In this tutorial i will explain details about TMD PDU, UMD PDU, AMD PDU AMD PDU Segment and STATUS PDU.
Power Headroom Report MAC control element tells if UE can transmit at a higher transmission power or not. In basic terms this indicates how much relative transmission power left in the UE.
So a simple formula for Power Headroom in LTE is
Power Headroom = UE Max Transmission Power – PUSCH Power = Pmax – P_pusch
So if Power Headroom is a positive value, that means UE is still capable to send at higher Tx power or it is capable of transmitting at higher throughput. If the value is negative, UE is already transmitting at maximum Tx power.
In the positive Power Headroom case, network may allocate more resource blocks to the UE, but in the negative Power Headroom case it is assumed that UE is already using the maximum resource blocks and no need to assign more.
While studying the MAC specification today, I thought it would be a good idea to check the MAC Buffer Status Report (BSR) control element details.
I had following questions in my mind about Buffer Status Report:
- Why is this control element used in LTE?
- What are different BSR CE formats?
Internet of Things is the buzzword and there is no doubt in that in one way or another we all are going to be part of the connected world where not only individuals but practically everything will be connected.
But the real question is HOW. Which technology will be the major backbone for this paradigm shift in wireless communication when neither voice nor data throughput become the primary concern, but connectivity. Can LTE solve the real world problems which will arise because of millions or even billions of connected nodes and individuals?
In a new study by GSMA it is estimated that IoT will drive the device connection density to the extreme, eventually reaching 200,000 connections per km². Which will generate a significant signalling load for the network if a connection oriented technology such as LTE is used. Along with that the new device to device communication puts new requirements for reduced latency, improved reliability, longer battery life for devices and more consistent user bit rates.
Future of Mobile/Wireless Computing
Mobile phone users worldwide 2012 to 2018 (in billions)
This tutorial explains how LTE downlink maximum throughput is determined. This is a simple and straightforward formula for data rate calculation.
The maximum data rate depends on channel bandwidth. As LTE uses different channel bandwidths both for FDD and TDD.
Let’s take the example for LTE using FDD, where channel bandwidth can be 5 MHz, 10 MHz and 20 MHz. In LTE release 8 there is no carrier aggregation, so let’s just consider simple cases.