Understanding Hierarchical Modulations, what is interlayer interference and how to quantify it: II Effective Signal-to-Noise Ratio (ESNR)

[Understanding Hierarchical Modulations: I Introduction]
[Understanding Hierarchical Modulations: III Modulation Efficiency]
S. Wang and B. K. Yi, "Optimizing Enhanced Hierarchical Modulations," IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, New Orleans, LO, 2008, pp. 1-5
[How to Broadcast Multimedia Contents? II Lessons from The Channel]
[How to Broadcast Multimedia Contents? IV Hierarchical Modulation]
[How to Broadcast Multimedia Contents? V Overloaded Transmission and IC]
[How to Broadcast Multimedia Contents? VI Open-Loop MIMO for BCMCS]
[How to Broadcast Multimedia Contents? VII Network Layer or Steam Layer Design]

Besides the throughputs achievable by hierarchical modulations, it is also interesting to understand hierarchical modulations from a practical signal-processing perspective. At this time, the performance of hierarchical modulation will be evaluated through an actual implementation, where demodulation error is one of the major concerns. In general, it is difficult to give a simple closed-form BER or symbol-error rate (SER) expression for hierarchical signal constellation, which also depends on receiver design and bits-to-symbol mapping. The BER of square-shaped MQAM constellation and a hierarchical QAM constellation for maximum likelihood (ML) demodulator can be computed by using recursive algorithms [8]. For a simple QPSK modulation, it is known that the BER is  shown in the figure below.





From a signal processing standpoint, demodulation error and capacity degradation may happen when there is a change of interference distribution, even though the received SNR γ is the same. The BER performance of regular QPSK/QPSK becomes deteriorated in Fig. 7 when ζQPSK/QPSK increases. 





However, with optimally rotating the enhancement-layer signal constellation, the performance loss can be recovered. This kind of recovery is more significant with large ζ. 


In order to quantify and understand this kind of BER performance loss due to interference and receiver design, one approach we propose for capturing this kind of degradation is to calculate the effective signal-to-noise ratio (ESNR) of the whole transceiver chain, which is defined by


where Pe(γ) is the demodulation BER of the signal with SNR γ, and Ψ−1 (∗) denotes the inverse function of Ψ(·), the demodulation error probability function with no ILI. 

The ESNR for the QPSK-modulated base layer or enhancement layer of any hierarchical modulation can be calculated by





Comments

Post a Comment

Popular posts from this blog

Hack Apple TV for Watching Chinese TVs and Videos

Image
[ Hack Patriot Box Office for Watching Chinese Videos and TVs ] Figure 1.   Apple TV Apple TV (ATV) is a  multi-function set-top box  designed by Apple Inc. originally as a  networked media player  for streaming multimedia contents to a television or an external monitor.  Now, it seemingly evolves into a iPod Touch without a touch screen but with a relatively inexpensive MSRP price tag of $99.  (Indeed, if you have an old generation iPod Touch, you may think about mirroring or airplay it onto a television instead.)  On March 7, 2012, Apple Inc. released a  3rd generation ATV (ATV3)   that includes a 32 nm ARM Cortex-A9 Apple A5 SoC (the same process as used in a 5th generation iPod Touch, a new iPad 2 and an iPad Mini) and 512MB mobile DDR2 memory (the same amount of memory as used in an iPhone 4).  An ATV3 has a buit-in 6 W power supply with no cooling fan necessary.  Unfortunately, until now, there is no public released jailbreak available for an ATV3, so modified software or
Read more

Hack Patriot Box Office for Watching Chinese Videos and TVs

As requested by friends, this blog is dedicated to explain a simple way for watching Chinese TV programs and movies on a television or monitor for free using a special media player instead of a computer.  Compared with many well-known approaches watching Chinese TVs on a computer, this one seems much more operation-friendly as well as eco-friendly.  It is attractive for many Chinese families who may not always be technical savvy.  In addition, as I know, the operation cost or power consumption of this kind of MIPS-based media players is relatively low.  Its total power consumption usually is no more than 15 watts.  Meanwhile, a typical power consumption of a PC CPU, even some mobile or laptop CPUs,  itself is known to be between 50 watts and 100 watts.  Even a power efficient Intel Atom CPU usually is inside a range between 5 and 20 watts, as I remember.  Nowadays a typical home desktop demands a power supply of no less than 250 watts, not to mention that a powerful game desktop or wo
Read more

How to Broadcast Multimedia Contents? II Lessons from The Channel

Image
What Is The Next for Mobile System Design? I A Single-Cell Model Perspective on Downlinks [How to Broadcast Multimedia Contents? I Introduction] [How to Broadcast Multimedia Contents? IV Hierarchical Modulation] [How to Broadcast Multimedia Contents? V Overloaded Transmission and IC] [How to Broadcast Multimedia Contents? VI Open-Loop MIMO for BCMCS] [How to Broadcast Multimedia Contents? VII Network Layer or Stream Layer Design] COST 231 model, which was developed by European COST Action 231, and its variations are the most popular radio propagation model adopted in various standardization bodies, such as 3GPP, 3GPP2 and IEEE. Its modifications include COST 231-Hata Model and COST 231-Walfisch-Ikegami Model . The mathematical formulation of the COST 231-Hata model path loss in dB is PL = 46.3 + 33.9 logf - 13.82log h BS - a( h MS ) + [ 44.9-6.55logh BS ] log d + C which features a carrier frequency f between 800MHz and 2GHz, an above-neighborhood base station antenna w
Read more