Weightless-P TDMA Resource Workbench

Schedule Weightless-P devices across time slots and narrowband subchannels while watching latency, capacity, and sleep-time trade-offs

Learner-ready Weightless-P TDMA/FDMA workbench with a visual slot/subchannel scheduler, scenario presets, play/step/reset controls, payload airtime and duty-cycle readouts, diagnosis cards, technical guardrails, guided practice, and primary source links.

Weightless-P TDMA + FDMA LPWAN scheduler

Weightless-P TDMA resource workbench

Weightless-P is a scheduled LPWAN design: the base station coordinates when devices talk, and the uplink can divide spectrum into narrow 12.5 kHz subchannels or combine eight of them into a wider 100 kHz resource. Use the workbench to see how slot plans trade capacity, latency, airtime, and sleep time.

ScenarioPeriodic meter

Access mix8 x 12.5 kHz

Frame period300 ms

Radio awake9.3%

Beginner ramp

Read the schedule like a radio calendar

TDMA answers "when may I transmit?" FDMA answers "which narrow frequency slice do I use?" The schedule is efficient only when devices can sleep outside their assigned resources and still hear the next beacon or grant.

Base station leadsThe base station synchronizes devices, announces grants, and can reserve uplink or downlink opportunities.

Slots are teaching unitsThe slider uses a visible slot duration so the math is inspectable. It is not claiming one fixed Weightless-P slot length.

Subchannels add capacitySeveral devices can use the same time slot if they are placed on different narrowband subchannels.

Low power needs silenceA device saves energy when it wakes for its beacon, grant, packet, and acknowledgement window, then sleeps again.

Scenario

Schedule Controls

Slots per teaching frame 12 slots 8 slots 12 slots 16 slots

Visible slot duration 25 ms

Uplink resource mode 8 narrow subchannels Narrow: 8 x 12.5 kHz Aggregate: 100 kHz

PHY data rate 5 kbps 0.625 kbps narrow 1.25 kbps narrow 5 kbps narrow 10 kbps narrow 6.25 kbps aggregate 12.5 kbps aggregate 50 kbps aggregate 100 kbps aggregate

Active devices 6 devices

Payload size 24 B

Unavailable subchannels 1 blocked

Acknowledgement policy scheduled ACK No ACK in this frame Scheduled ACK ACK plus retry reserve

Ready: inspect the scheduled resources.

Try First

Switch between narrow and aggregate mode. In narrow mode, capacity comes from many logical channels. In aggregate mode, one transmission can be faster, but it consumes the full 100 kHz resource during that slot.

slot wait resource use payload airtime awake fraction

Base Station Schedule Flow

beacon sync

Slot and Subchannel Map

Columns are time slots. Rows are 12.5 kHz subchannels. Blocked rows represent spectrum the planner avoids.

Device Grants

Click a device card to remove or restore that device's scheduled resource and watch the utilization and diagnosis change.

Readouts

300 msteaching frame period = slots x visible slot duration

150 ms avgaverage wait to the next matching frame opportunity

38.4 mspayload-only airtime lower bound at selected PHY rate

18%occupied time-frequency resource cells

77 freeunblocked cells left for other scheduled traffic

9.3%rough radio awake share for one assigned device

Diagnosis

Formula and Guardrail Trace

Question	Teaching calculation	Current result	Guardrail

Quick Reference

TDMATime Division Multiple Access. Devices use scheduled time opportunities instead of all transmitting whenever they like.

FDMAFrequency Division Multiple Access. A channel can be split into different frequency slices so simultaneous scheduled users do not collide.

12.5 kHz modeMore logical narrowband resources, lower selected data rates, and better scheduling density for many small uplinks.

100 kHz aggregateEight 12.5 kHz subchannels are combined for higher data rate, consuming the wider resource for that slot.

Guided Practice

1. Dense meter fleetChoose Dense fleet, then compare narrow and aggregate mode. Which one leaves more free scheduled resources?

2. Coverage edgeChoose Coverage edge and lower the data rate. Watch payload airtime rise and decide whether the slot plan is still realistic.

3. Alarm priorityChoose Alarm burst and turn on ACK plus retry reserve. Notice how reliability consumes extra downlink and retry capacity.

Technical Accuracy Notes

This is a teaching scheduler, not a Weightless-P conformance test. The visible slot length and frame size are adjustable so learners can compare timing trade-offs; real systems depend on the exact PHY mode, MAC configuration, regional band rules, traffic profile, and implementation.

The model uses source-backed Weightless-P facts: the uplink combines TDMA and FDMA, 12.5 kHz is the unit narrowband subchannel, scheduled uplink can use a single 12.5 kHz subchannel or combine eight subchannels into 100 kHz, and the published PHY data rates span narrow and aggregate modes. The payload airtime shown is a lower bound because real packets include synchronization, coding, headers, acknowledgements, retransmissions, and guard time.

Do not read "TDMA" as "free of regulation." Unlicensed sub-GHz deployments still have local power, duty-cycle, channel, and listen-before-talk rules. Also separate technical capability from market maturity: Weightless-P is useful as an LPWAN scheduling example even though its commercial ecosystem is much smaller than LoRaWAN or cellular IoT.

Primary Sources and Related Pages

Weightless-P System Specification System design overview and PHY/MAC details used for the TDMA/FDMA, 12.5 kHz, 100 kHz, and data-rate guardrails. Weightless-P specification summary Weightless product summary covering FDMA+TDMA, narrowband channels, adaptive data rate, time synchronization, and QoS. Weightless course chapter Local IoTClass background on Weightless-W, Weightless-N, Weightless-P, and ecosystem trade-offs. LPWAN technology selector Compare scheduled Weightless-P behavior with LoRaWAN, Sigfox, NB-IoT, and LTE-M deployment choices.