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.
A few weeks ago I was looking into an issue related to E911 or Emergency call over the IMS network. Though it appears as most of the concepts related to emergency calls are still same in IMS as compared to legacy systems, such as 3G and GSM, there are many new things are added for IMS.
Both in UMTS and GSM and other CS based systems emergency call was often referred to speech calls, but the IP Multimedia Subsystem(IMS) supports different other types of media along with speech calls. When other media types are used during an emergency session, it is referred as IMS Multimedia Emergency Session (MES).
As usual whenever the user calls an emergency number by default the call is routed to the emergency service.
Let’s find it out what different media types an IMS UE supports during a E911 session towards IP PSAPs (emergency response centre).
- Real time video both simplex and fullduplex
- Text-messaging (Similar to SMS)
- File transfer
- Video clip sharing, picture sharing, audio clip sharing