Home / WIMAX / Page 6

Evolution of Broadband Wireless

The history of broadband wireless as it relates to WiMAX can be traced back to the desire to find a competitive alternative to traditional wireline-access technologies. Spurred by the deregulation of the telecom industry and the rapid growth of the Internet, several competitive carriers were motivated to find a wireless solution to bypass incumbent service … Read more

How Open-Loop Transmit Diversity in Wimax?

Transmit spatial diversity is a newer phenomenon than receive diversity and has become widely implemented only in the early 2000s. Because the signals sent from different transmit antennas interfere with one another, processing is required at both the transmitter and the receiver in order to achieve diversity while removing or at least attenuating the spatial … Read more

Interference Limited MIMO Systems for Wimax

The third assumption—that the background noise is Gaussian and uncorrelated with the transmissions—is especially suspect in a cellular MIMO system. All well-designed cellular systems are by nature interference limited: If they were not, it would be possible to increase the spectral efficiency by lowering the frequency reuse or increasing the average loading per cell. In the … Read more

Spatial Multiplexing and Receiver Gains in Wimax

Spatial Multiplexing In a multipath environment, the data rate increase due to MIMO is equal to the number of MIMO antennas. Rather than to transmit the same bit of more than two antennas, the Spatial Multiplexing method sends a data bit from the first antenna, and another bit of the second antenna at the same … Read more

Receive Diversity Selection and Switched Diversity

Make use of a number of receive antennas that are well separated (coherence distance) to generate independent receptions of the transmitted signal. Selection diversity: choose received signal with largest received power, S/N, etc. Switched diversity: choose alternate antenna if signal falls below a certain threshold. Linear combining: linearly combine a weighted replica of all received … Read more

Types of Diversity Space, Time, Spatial, Frequency and Polarization

We know that we normally have several independent paths from TX to Rx of different lengths, these are affected and delayed differently, Signals that start out together at the transmitter will be separated in time when they reach the receiver Diversity doesn’t work with Line of Sight, This is exploiting Multipath rather than fighting it … Read more

What are IP Multimedia Subsystem IMS and IMS Structure

IMS means IP Multimedia Subsystem is an essential part of the all-IP UMTS architecture and Relevant for WiMAX for the same usage and also for WiMAX to UMTS Interworking. This is part of the WiMAX Forum architecture. IP Multimedia Subsystem (IMS) is a Service Delivery Architecture and standardized architecture to provide Internet Protocol (IP)-based mobile … Read more

IP Multicast Service Models – Dense and Sparse Modes

IP Multicast Service Models Having Three Multicast Any-Source Multicast (ASM) Source-Filtered Multicast (SFM) and Source-Specific Multicast (SSM) which work as below. Any-Source Multicast (ASM) Destination ‘multicast’ address only defines ‘Group’ membership Will accept from ‘any source’ (unicast) First and oldest model, defined in RFC 1112 Source-Filtered Multicast (SFM) Destination ‘multicast’ address only defines ‘Group’ membership … Read more

Multicast Advantages and Disadvantages

When sending the same data to multiple receivers, rather than send multiple copies all the way from sender to all the receivers, just send one copy and duplicate where paths diverge Better bandwidth utilisation Less host/router processing Receivers’ addresses may be unknown A possible thing to use for IPTV over WiMAX. Multicast Advantages Enhanced Efficiency: … Read more

Why IP Addresses? Why private and public both IP address needed?

IP Networks use Routers to do the switching based on IP addresses, Layer 3 routing protocols like BGP or OSPF an Ethernet networks use 48 bit MAC addresses Spanning Tree is used to route because users, base stations, routers, etc will all need IP addresses (It is an IP-based system) There are Public (Internet routable) … Read more