Half Rate is a speech coding

Speech coding

Speech coding is the application of data compression of digital audio signals containing speech. Speech coding uses speech-specific parameter estimation using audio signal processing techniques to model the speech signal, combined with generic data compression algorithms to represent the resulting...

 system for GSM, developed in the early 1990s.

Since the codec

Codec

A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...

, operating at 5.6 kbit/s, requires half the bandwidth

Bandwidth (computing)

In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...

 of the Full Rate

Full Rate

Full Rate or FR or GSM-FR or GSM 06.10 was the first digital speech coding standard used in the GSM digital mobile phone system. The bit rate of the codec is 13 kbit/s, or 1.625 bits/audio sample...

 codec, network capacity for voice traffic is doubled, at the expense of audio quality. It is recommended to use this codec when the battery is low, it saves 30% energy. The sampling rate is 8 kHz with resolution 13 bit, frame length 160 samples (20 ms) and subframe length 40 samples (5 ms).

GSM Half Rate is specified in ETSI

European Telecommunications Standards Institute

The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...

 EN 300 969 (GSM 06.20), and uses a form of the VSELP

Vector Sum Excited Linear Prediction

Vector sum excited linear prediction is a speech coding method used in several cellular standards. The VSELP algorithm is an analysis-by-synthesis coding technique and belongs to the class of speech coding algorithms known as CELP .Variations of this codec have been used in several 2G cellular...

 algorithm. Previous specification was in ETSI ETS 300 581-2, which first edition was published in December 1995.

For some Nokia phones you can configure the use of this codec:

• To activate HR codec use enter the following code: *4720#
• To deactivate HR codec use enter the following code: #4720#

See also

• Full Rate
  Full Rate
  Full Rate or FR or GSM-FR or GSM 06.10 was the first digital speech coding standard used in the GSM digital mobile phone system. The bit rate of the codec is 13 kbit/s, or 1.625 bits/audio sample...
  
  
• Enhanced Full Rate
  Enhanced Full Rate
  Enhanced Full Rate or EFR or GSM-EFR or GSM 06.60 is a speech coding standard that was developed in order to improve the quite poor quality of GSM-Full Rate codec. Working at 12.2 kbit/s the EFR provides wirelike quality in any noise free and background noise conditions...
  
   (EFR)
• Adaptive Multi-Rate
  Adaptive Multi-Rate
  The Adaptive Multi-Rate audio codec is a patented audio data compression scheme optimized for speech coding. AMR was adopted as the standard speech codec by 3GPP in October 1999 and is now widely used in GSM and UMTS...
  
   (AMR)
• Adaptive Multi-Rate Wideband (AMR-WB)
• Extended Adaptive Multi-Rate - Wideband (AMR-WB+)

External links

• ETSI EN 300 969 - Half rate speech transcoding (GSM 06.20 version 8.0.1 Release 1999) - technical specification
• ETSI ETS 300 581-2 - Half rate speech transcoding (GSM 06.20 version 4.3.1) - obsoleted
• RFC 5993 - RTP Payload format for GSM-HR