HaLow Scale And RAW Windows

Ada re-derives this chapter’s own numbers step by step, at full precision

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Ada ADA · CALCULATION AUDIT

HaLow Scale And RAW Windows

A smart-agriculture site spreads 2000 soil sensors across several hectares, and ordinary 2.4 GHz Wi-Fi cannot cover that range or device count from one access point. The chapter’s answer is a single HaLow access point that claims to track all 2000 stations using a 13-bit association ID and Restricted Access Window grouping. This audit asks the question that claim invites: do the addressing capacity and the RAW schedule actually support 2000 stations, or is the 8191-station ceiling just an address count?

Companion to the chapter Wi-Fi HaLow (802.11ah) for IoT — every number here comes from that chapter.

Ada: HaLow’s scale claim is not magic; it is addressing capacity plus scheduled contention. The chapter gives enough values to check both without inventing a data rate or battery-life number.

  • A 13-bit AID field gives 2^13 = 8192 possible codes. With one code unavailable for ordinary station identity, the usable ceiling is 8192 - 1 = 8191 stations per AP.
  • The worked site has 2000 soil sensors, so the association ledger uses 2000 / 8191 = 0.244, or about 24.4% of that address space. It leaves 8191 - 2000 = 6191 station identities, but address headroom is not airtime proof.
  • The channel-width set is 1, 2, 4, 8, 16 MHz; the widest listed channel is 16 / 1 = 16 times the narrowest. That is a width trade, not a universal range or throughput guarantee.
  • RAW grouping checks the contention pool: 2000 sensors split into 20 groups gives 2000 / 20 = 100 sensors per group.
  • The same plan is 20 separate windows because 2000 / 100 = 20. During one RAW window, only 100 / 2000 = 0.05, or 5%, of the fleet is eligible to contend.
  • The scheduling reduction is 2000 / 100 = 20x: the AP has changed one large collision pool into twenty smaller pools. The release still needs measured retry, missed-window, downlink, and maintenance-update evidence.

The audit conclusion is bounded: the 13-bit AID explains the 8191 station ceiling, and 20 RAW groups of 100 sensors reduce per-window contention by 20x. Those calculations support a scale review, not an approval, until installed logs show the wake schedule and service traffic actually hold.

Every number above is taken from the chapter’s own material and re-derived step by step.