The mobile network radio interface requires a sync stability of 5x10-8s. Such stability cannot currently be provided while connecting Node X via a packet switched network like WiMAX. It hence seems that synchronization can be a serious blocking factor for using WiMAX as a UTRAN backhauling system. Fortunately there are 3 candidate solutions that can overcome this issue. These are NTP, IEEE 1588 and SYNCoIP. The reference is transported over IP in ‘CE’ style. It is very QoS dependent and development is not finalized. However the required accuracy is achieved and relied on IP only and is developed from existing techniques.
For modeling traffic, coverage and capacity cannot be separated -traffic has to be considered in network planning.
Multiple knapsack- For rough capacity estimations the soft capacity feature of the WCDMA is sometimes neglected. Instead each cell is assumed to have a fixed capacity v. The capacity value can be considered an amount of Erlang that the cell can support. The set of demand points assigned to one cell can then easily be required to generate no more than v units of traffic.
A single, linear constraint of the type in the above with positive co effectiveness is called a knapsack constraint- multiples are derived from them.
Receiver performance related to the sensitivity level and thermal noise (spectral density, Boltzmann constant –from statistical physics ……..receiver sensitivity level in dBm =
The Network Simulator also known as - ns-2.Ns is a discrete event simulator targeted at networking research. Ns provides substantial support for simulation of TCP, routing, and multicast protocols over wired and wireless (local and satellite) networks.
i was designing around WiMAX components to look for low noise designs for RF transceivers. The CHIP of my interest is MAX2839. The great thing about MAxim is you can request for samples and they have excellent technical support..a great company !
The MAXIM semiconductors MAX2839 direct conversion, zero-IF, RF transceiver is designed specifically for 2GHz 802.16e MIMO mobile WiMAX systems. The device incorporates one transmitter and two receivers, with > 40dB isolation between each receiver. The MAX2839 completely integrates all circuitry required to implement the RF transceiver function, providing RF to baseband receive path, and baseband to RF transmit path, VCO, frequency synthesizer, crystal oscillator, and baseband/control interface. The device includes a fast-settling sigma-delta RF synthesizer with smaller than 40Hz frequency steps and a crystal oscillator that allows the use of a low-cost crystal in place of a TCXO. The transceiver IC also integrates circuits for on-chip DC-offset cancellation, I/Q error, and carrier leakage detection circuits. An internal transmit to receive loopback mode allows for receiver I/Q imbalance calibration. The local oscillator I/Q quadrature phase error can be digitally corrected in approximately 0.125° steps. Only an RF bandpass filter (BPF), crystal, RF switch, PA, and a small number of passive components are needed to form a complete wireless broadband RF radio solution.
The CHIP completely eliminates the need for an external SAW filter by implementing on-chip programmable monolithic filters for both the receiver and transmitter, for all 2GHz and 802.16e profiles and WIBRO. The baseband filters along with the Rx and Tx signal paths are optimized to meet the stringent noise figure and linearity specifications. The device supports up to 2048 FFT OFDM and implements programmable channel filters for 3.5MHz to 20MHz RF channel bandwidths. The transceiver requires only 2µs Tx-Rx switching time.
Excellent results were obtained in the Korean WIBRO Systems and 802.16e Mobile WiMAX Systems.
what is ur opinion about the future of the wimax in comparison
with the 3G.
and can we make use of the wimax as an standard air interface
and what about the job oppertunities in usa.
LTE, combining OFDM and MIMO, will provide on 2 to 5 times greater spectral efficiency than the most advanced 3G networks, reducing the cost per bit and allowing better economics for operators and end users.
OFDM as we all know splits the information into multiple narrowband subcarriers, allowing each of them to carry a portion of the information at a lower bit rate, which makes OFDM a very robust modulation, particularly in multipath scenarios, like urban areas.
Also MIMO technology creates several spatial paths on the air interface between the network and the subscriber; so these paths can carry the same or different streams of information, allows an increase in either the coverage (due to higher Signal to Noise Ratio (SNR) at the receiver) or the user data throughput.
The result is affordable mass market wireless broadband services that will boost Operator profitability. Faster downloads, video sharing, true Mobile TV with more channels and enhanced quality are just some examples of applications that will benefit from LTE's greater performance.
I was researching the possibility of using wiMAX for backhauling remote areas. I was hoping that 802.16m would meet the bandwidth requirements to provide 10-12 Mbps to customers in rural areas. This is based on the australian governments's NBN initiative.
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