Short range connectivity options for IoT

Here’s all you need to know about short-range wireless technology options for IoT.

Jayasimha Holkal Jan 27th 2017

The concept of connecting devices to the Internet is called, the Internet of Things (IoT). While, traditionally, computers and mobile phones were connected to the Internet, IoT has evolved to encompass various consumer electronic devices such as refrigerators and televisions as well as automobiles such as smart trucks and connected cars that are, now, getting connected to the Internet. There are two major mechanisms by which these end devices can have wireless access to the Internet:

  • Directly: Through inbuilt Modem or LPWA (Low Power Wide Area) module
  • Indirectly: Through inbuilt Wireless Module connected to a Gateway/Access Point

I am going to focus on the indirect method, specifically where short-range wireless technologies are used. We will look at the options/technologies available and currently being used for connecting devices to Internet and compare them based on a set of parameters.

The short range wireless technologies that we will be considering for this comparison are:

  • Wi-Fi
  • Bluetooth (BR/EDR)
  • Bluetooth Low Energy (BLE)
  • ZigBee
  • Z-Wave

Following are the parameters considered for comparison in this article:

  • Power Consumption
  • Throughput
  • Cost
  • Range
  • Topology
  • Internet Connectivity

Power Consumption

Though many IoT devices like coffee makers, smart bulbs, etc. could be powered by mains, power consumption would be an important consideration for other devices such as battery-powered door locks. The power consumption of the overall solution relative to the communication module would also be a factor in considering the technology to be used.

Among these technologies considered, Wi-Fi’s power consumption is much higher than Bluetooth’s and both of these consume more power than Z-Wave, ZigBee and BLE. Power saving modes provided by these technology standards have to used and tuned to particular requirements to optimize power consumption.

Throughput

While wireless communication technologies are compared by their PHY bit rate, additional factors, mentioned below, have to be considered while designing a solution.

Technology

Max Bit Rate

WiFi a/b/g

54 Mbps

Bluetooth

3 Mbps

BLE

1 Mbps

ZigBee

250 kbps

Z-Wave

100kbps

Table 1: Comparison of PHY Bit Rates of various technologies

  • Actual bit rates: This is the actual bit rates at baseband level excluding guard intervals, acknowledgements, fixed slot sizes, etc. It could be much less than PHY bit rate and would also have dependency on the packet size used. For example: Bluetooth EDR specifies upto 3 Mbps bit rate, but considering the max packet size (3-DH5) and asymmetric flow, the maximum bit rate at baseband layer is only 2.178 Mbps.
  • Channel sharing: The airtime/channel would be shared by the devices that are connected or available on the physical channel. This would effectively reduce the throughput available for each device. Additionally, in case of mesh scenarios, the channel is shared multiple times as the packet traverses through different nodes.
  • Protocols: There would be overheads for the various underlying protocols in terms of their header information, acknowledgement packets, re-transmissions, etc. that would effect the throughput rates.
  • Co-existense/Interference: Throughput could get affected by th coexistense of different networks, either of the same technology or of different technologies but in the same band.

Cost

This section considers the cost of the modules/chipsets. Solutions may be of two types:

  • Wireless transceiver (controller) as a separate chipset
  • Single chipset solution where there is an embedded CPU for hosting stack and application


The solution may be built using  a Module containing the chipset or be built of discrete components.

The following Tables 2 and 3 provide the cost of the various chipsets/modules.[1] 

Table 2: Single Chipset Solution

Table 3: External MCU Required

Technology

Chipset

Chipset Cost

Module Cost

Wi-Fi

CC 3200

5.54

9.99

BLE

CC2541

1.79

 
 

CC 2640

2.5

6.7

ZigBee

CC 2630

2.65

 

Z-Wave

ZM5202

 

6.04

 

Technology

Chipset

Chipset Cost

Module Cost

Wi-Fi

CC 3100

3.99

7.99

 

WL 1801

 

9.99

BT (Traditional)

TI CC2560

1.86

 

 


Range and Topology

Range not only depends upon Tx power and Rx sensitivity but also on the obstacles. Line-of-sight (outdoor) range is much better than indoor. Sub-GHz range is better than 2.4 GHz, which in turn is better than 5 GHz. Typical indoors and outdoors ranges, bands used, and topologies are shown for various technologies in Table 4. Mesh and Tree topologies extend the range.

Technology

Bands (GHz)

LoS Range

Indoors

Topologies

Wi-Fi

2.4, 5

100m

10-30m

Star/Mesh

BT Traditional

2.4

30m

5-10m

Star

BLE

2.4

50m

5-15m

Star

ZigBee

2.4

30m

5-15m

Star/Mesh/Tree

Z-Wave

Sub GHz

30m

10-15m

Star/Mesh/Tree

Table 4: Comparison of ranges, bands and topologies of various technologies

 

Note:

  • Upcoming Wi-Fi – HaLo specification intends to use sub-GHz
  • These ranges are for point-to-point connections. These can be extended with Mesh (ZigBee/Z-Wave)
  • Upcoming BLE specifications would support Mesh
  • Z-Wave supports Mesh upto a depth of 4

Internet Connectivity

Devices using Wi-Fi would be able to access the Internet through Access Point/Gateways. A HTTP client in the device could directly access a website/server through the Access point.

Though Bluetooth and BLE can provide IP access through PAN and IPSP profiles and other Bluetooth transports, profiles defined for various use cases cannot be leveraged over this connection. A Gateway application has to be used to solve this problem. Similarly, ZigBee Gateway application has to be written to send ZigBee cluster/attributes information over the Internet. ZigBee also defines ZIP (ZigBee IP Network), an IPV6 and 6LowPAN based network layer over 802.15.4. Today, only Smart Energy 2.0 profile uses ZIP.

Z-Wave supports Z/IP router, Gateway, and IPv6. Z-Wave supports transmission of Command Class over IP network. It uses a UDP port for transmitting Z-Wave Home Automation Command Class packets. Z/IP Gateway supports transmission of the packets received over IP to classic Z-Wave devices.

Others

Some other parameters that are key in taking a descision are security, ease of commissioning, eco-system support, certification costs, and interoperability. Some of the other connectivity technologies that can be considered are NFC, Thread, ANT, etc.

The author is Senior Architect-Software, Product Engineering Service at Sasken

Disclaimer: This article is published as part of the IDG Contributor Network. The views expressed in this article are solely those of the contributing authors and not of IDG Media and its editor(s).