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LOS vs NLOS | Difference between LOS and NLOS wireless channels

This page compares wireless LOS vs NLOS channel and mentions difference between LOS and NLOS. LOS stands for Line of Sight and NLOS stands for Non Line of Sight. Link to wireless channel models are also mentioned. Refer types of channel models>> used in wireless signal propagation.

LOS-Line of Sight Channel

LOS-Line of Sight

As mentioned LOS stands for Line of Sight. The figure-1 depicts line of sight communication between two transceivers. This LOS deployment is possible when there is no obstruction between base station (BS) and mobile/fixed subscriber stations (SSs). In other words, LOS communication is possible when there is no obstruction between transmitter and receiver. Due to less attenuation in the LOS communication, it offers good signal strength and higher amount of throughput compare to NLOS counterpart.

Examples of LOS wireless link:
• Microwave point to point communication
• point to point connection between BS and SS.

NLOS-Non Line of Sight Channel

NLOS-Non Line of Sight

As mentioned NLOS stands for Non Line of Sight. The figure-2 depicts NLOS deployment scenario. As shown, wireless link is considered to be NLOS when natural and/or man made structures block the path between base station and subscriber stations. In other words, NLOS communication is possible even when there is obstruction between transmitter and receiver. The signal arrives to the receiver after going through many obstructions in between. On the path, signal goes through attenuations as well as reflection, diffraction as well as penetrations.
Refer Reflection vs Diffraction >>.

In NLOS case, wireless link can only be established if reflective path exists between base station and subscriber station as shown.

Due to NLOS, multiple copies of signals arrive at different times with different amplitudes. This results in ISI/ICI. This problem is avoided with the use of OFDM and OFDMA techniques along with cyclic prefix. The cyclic prefix length is kept greater than delay spread value to overcome ISI/ICI. The OFDM/OFDMA techniques have become very popular and are in use in many modern wireless communication systems such as WiMAX, WLAN, LTE, LTE-Advanced and more.

Examples of NLOS wireless link:
• Wireless connection between BS (Base Station) and SS (Subscriber station) / MSS (Mobile Subscriber Station)

DOWNLOAD CHANNEL MODEL MATLAB CODES

Following are matlab codes for channel models viz. SUI channel model, ITU-T channel model as per wimax 802.16e standard, JTC channel model as per 802.11b/11g, UWB channel model as per 802.15.3 and 802.15.4 standard specifications. 802.11a WLAN channel model matlab files
802.11b 11g JTC WLAN channel model matlab files
802.15.3 UWB channel model matlab files
802.15.4 UWB channel model matlab files
802.16d SUI WiMAX channel model matlab files
802.16e ITU-T channel model matlab files
Rayleigh channel model matlab files
Rician channel model matlab files

RF and Wireless Terminologies


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