We’re currently working with customers in the TCF to implement a change in band plan from 997 to 998 for VDSL, which will increase coverage and speed for a majority of your customers. We have completed lab testing of those modems supplied to us and would like to share an overview of the results with you and let you know our next steps.

What's happening?

In January (Informer 240) we asked customers to send us their VDSL modems so we could test them to ensure that when the existing VDSL 997 DSLAM profiles are updated to 998 your VDSL modems will switch over and continue to operate at a similar or better overall performance.

The modem lab testing is now complete with results showing that all modems tested will auto re-sync from 997 to 998 and at most distances and profiles provide a better overall performance. Once we have agreement from the TCF VDSL working party members our next step is to complete field testing to validate the results with real world performance

What's the detail?

The modems supplied were tested to the agreed Modem Test Plan, which tested all modems on 997 and 998 using the network profiles 17a and 8b, with our two VDSL cards and at distances 100, 800 and 1000m.

We observed the following lab test results:

• Increased download speeds – all tested distances showed better downstream performance on 998.
   
• Increased upload speeds – short tested distances showed a much better upstream performance on 998 due to the removal of the 10Mbps upload restriction. The long tested distances showed in most cases a slightly slower upstream performance. This is expected as 998 is more asymmetric, with some upstream channels being utilised for downstream.
   
• Increased coverage – with the improved downstream performance on 998 at longer distances, we should be able to increase the coverage of VDSL.  This will be confirmed by field testing.
   
• Consistent re-synch – all modems auto re-synched from 997 to 998 with no change in synch times observed. The average synch time was less than 5 minutes.
   
• Only VDSL services impacted - when the updated 998 profiles were deployed to a DSLAM, only VDSL services on that DSLAM were affected by the change and experience a modem re-synch. All other ADSL and ADSL2+ services on the DSLAM are unaffected.
   
• Card and profile differences – for the two different generations of VDSL linecards that we have deployed in our network the testing showed that one of our cards had less of an overall performance increase with the band plan change. Our two profiles also had differences in performance and we are in the process of deciding whether we will continue to use both of these profiles once 998 band plan is adopted.

Field testing

We expect the lab test results will be reflective of the real world performance but want to confirm this with field testing in June and July.

We propose two stages to the field testing, initially changing a total of 20 cabinets to 998 across four weeks, impacting approximately 900 VDSL connections and 20 customers.

Following the successful outcome of the first stage a further 90 sites both urban and rural will be changed, with field testing completing in July.

These changes will be deployed during normal maintenance windows and notifications will be provided via the planned notification process.
 

Next steps

1. Modem testing results - If you provided a modem for testing, we will send your modems specific test results today.  

2. Field testing – we will contact you directly if your customers are impacted by the initial five cabinets included in the proposed field testing.
3. Approval to change to 998 – on successful completion of field testing of 998 band plan and subject to customer agreement via TCF VDSL working party, we will seek, on behalf of the industry, approval from the Commerce Commission to change the VDSL standard for New Zealand to 998.
4. Migration to 998 - once the band plan for VDSL is formally changed to 998 the New Zealand wide migration will commence, this is estimated to commence mid-August and complete mid-November 2015.

Who do I contact?

For more information, please contact your Service Delivery Manager.