Well wat 70% means is tht when 70% of channel has been utlised and new assignment is to be done. it will be on HR rate and if now the traffic channel below 70% are occupied the tracffic chanel assigned will be FR.
abt AMR and NAMR, they hav diff thresholds for HR/FR assignment, tht is characterised by type of MS used.
As said by Bilal, there are two ways of implementing HR in ericsson 1. HR allocation(new assignments)here at the time of assignment the channel decision is made and 2. HR adaption (existing calls channel can be changed during an ongoing call becoz of radio quality.