Understanding IBSS (Ad-Hoc) Mode in Wi-Fi Networks

1. Basic Concept of IBSS

In wireless networks, IBSS (Independent Basic Service Set) is a network topology defined by the IEEE 802.11 standard, also known as Ad-Hoc mode. Unlike the common Infrastructure Mode, IBSS allows multiple devices to communicate directly without the need for an Access Point (AP), forming a temporary peer-to-peer network. This mode is particularly suitable for temporary networking, emergency communication, or direct data transfer between devices.

2. Working Principle of IBSS

1. Network Establishment

• • Device Initiation: A device actively creates an IBSS network, setting the SSID (ESSID), channel, encryption method, etc.
• • Joining Devices: Other devices scan for the IBSS network and join to start communication.

2. Data Transmission

• • CSMA/CA: Uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism to prevent data collisions.
• • No Central Scheduling: Devices negotiate to decide who can send data at what time, without AP coordination.

3. Network Identification

• • BSSID: In IBSS, the BSSID is typically a randomly generated MAC address (not the MAC of an AP), used to identify the network.
• • ESSID: A user-defined network name (SSID) used to identify the IBSS network.

3. Configuration Method of IBSS

In Linux systems, the IBSS network can be configured using the iw command, as described in the command line format.

1. Check Wireless Card Support

iw list | grep "Supported interface modes" -A 10

The output should include <span>IBSS</span> indicating support for Ad-Hoc mode.

2. Create IBSS Network

# Assuming the wireless interface is wlan0
# Disable the interface
sudo ip link set wlan0 down
# Set IBSS mode
sudo iw dev wlan0 set type ibss
# Enable the interface
sudo ip link set wlan0 up

# Create IBSS network (specifying SSID and channel, 2412MHz=channel 1)
sudo iw dev wlan0 ibss join MyAdHocNetwork 2412

3. Configure IP Address

# Manually set IP
sudo ip addr add 192.168.1.100/24 dev wlan0
sudo ip link set wlan0 up

# Automatically obtain IP, ensure a DHCP server is running on one node (ensure on the same subnet)
sudo dhclient wlan0

4. Join Existing IBSS Network

# Scan for IBSS networks
sudo iw dev wlan0 scan | grep -i "ibss"

# Join an existing IBSS network
sudo iw dev wlan0 ibss join MyAdHocNetwork 2412

5. Check Connection Status

iw dev wlan0 link

# View IBSS network information
iw dev wlan0 info
iw dev wlan0 station dump

4. Characteristics and Limitations of IBSS

Feature	Description
✅ No AP Required	Suitable for temporary networks, emergency communication, etc.
✅ Quick Deployment	Can establish a communication network within minutes.
❌ No Central Management	Lacks centralized control, resulting in lower network stability.
❌ Limited Performance	As the number of devices increases, collisions and delays increase.
❌ Low Security	Does not support WPA/WPA2, typically uses WEP or no encryption.
❌ Distance Limitations	All devices must be within each other’s communication range.

5. Typical Application Scenarios

Scenario	Description
Conference Collaboration	Temporary file sharing, screen projection.
Emergency Communication	Emergency networks during natural disasters or network outages.
IoT Device Interconnection	Direct communication between local devices without relying on the cloud.
Gaming Battles	Local multiplayer games, such as LAN games.

6. IBSS vs Wi-Fi Direct (P2P)

Feature	IBSS (Ad-Hoc)	Wi-Fi Direct
Network Structure	Fully peer-to-peer network	Introduces Group Owner (GO), similar to AP
Encryption Support	Only supports WEP or no encryption	Supports WPA2
Device Connection	All devices communicate directly	Data is forwarded through GO
Applicable Scenarios	Temporary, small networks	More complex scenarios requiring security
Standard Support	IEEE 802.11a/b/g/n/ac	Wi-Fi Alliance standards

7. Conclusion

IBSS (Ad-Hoc) is a wireless network mode that does not require an access point, suitable for temporary communication and small device interconnections. Although it is flexible to deploy and does not require infrastructure, it has significant limitations in terms of security, performance, and scalability. If you need a more stable and secure point-to-point connection, Wi-Fi Direct is a better choice.

If you are developing embedded devices, IoT systems, or need temporary networking, IBSS is still a foundational network mode worth understanding, as it has practical value in specific scenarios.

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