title: In-kernel passive measurement of the performance impact of hidden terminals in 802.11 wireless networks

authors: Raynel, Scott McKenzie

subjects: computer science

abstract: The negative performance impact of the presence of hidden terminals in wireless networks has been well know for decades. Despite much research in the area, many deployed networks continue to suffer a performance penalty because of hidden terminals. Ad hoc wireless networks are particularly susceptible to hidden terminal collisions because there are fewer opportunities to plan the network in a way that avoids or reduces the number of hidden terminals. Measuring the presence of hidden terminals and the impact they are having on performance is difficult, especially in a network of many nodes. Without such measurements, the users and operators of wireless networks can not tell if performance problems are caused by hidden terminals or some other problem. We introduce new methodology that can detect the presence of hidden terminals and estimate the performance impact they are causing. The methodology requires no additional hardware and is suitable for wide scale deployment and long term operation. The approach is based on in-kernel instrumentation of the wireless network stack. The design, implementation, and testing of the approach are covered. Results from in-lab testing and the measurement of a live commercial 802.11 network are also presented, including a case study where performance was significantly improved.

text: In-kernel passive measurement of the performance impact of hidden terminals in 802.11 wireless networks The negative performance impact of the presence of hidden terminals in wireless networks has been well know for decades. Despite much research in the area, many deployed networks continue to suffer a performance penalty because of hidden terminals. Ad hoc wireless networks are particularly susceptible to hidden terminal collisions because there are fewer opportunities to plan the network in a way that avoids or reduces the number of hidden terminals. Measuring the presence of hidden terminals and the impact they are having on performance is difficult, especially in a network of many nodes. Without such measurements, the users and operators of wireless networks can not tell if performance problems are caused by hidden terminals or some other problem. We introduce new methodology that can detect the presence of hidden terminals and estimate the performance impact they are causing. The methodology requires no additional hardware and is suitable for wide scale deployment and long term operation. The approach is based on in-kernel instrumentation of the wireless network stack. The design, implementation, and testing of the approach are covered. Results from in-lab testing and the measurement of a live commercial 802.11 network are also presented, including a case study where performance was significantly improved.

year: 2011

title: Niwashi - a new tool for pedology and cover-bed stratigraphy in New Zealand

authors: Lowe, David J.

abstract: The Japanese Niwashi - literally 'garden master' - is a new field tool for dressing soil profiles or cleaning down stratigraphic sections comprising sottish or unconsolidated cover-bed deposits. Used for many years by Japanese pedologists, tephrochronologists, and volcanologists, the Niwashi has now become available in New Zealand. We have tried it out on a range of soils and various deposits and found it to be an excellent tool for field work in many situations.

text: Niwashi - a new tool for pedology and cover-bed stratigraphy in New Zealand The Japanese Niwashi - literally 'garden master' - is a new field tool for dressing soil profiles or cleaning down stratigraphic sections comprising sottish or unconsolidated cover-bed deposits. Used for many years by Japanese pedologists, tephrochronologists, and volcanologists, the Niwashi has now become available in New Zealand. We have tried it out on a range of soils and various deposits and found it to be an excellent tool for field work in many situations.

year: 2000

title: Waata Kukutai: Rangatira o Ngaati Tiipa 1822-1867

authors: Ewe, Denise Te Tuhi

subjects: Biography

abstract: This thesis examines the life of Ngaati Tiipa rangatira Waata Kukutai (1822-1867), and critiques historical perspectives that have narrowly identified him as merely a Kuupapa loyalist. This study argues that Kukutai’s choices and leadership were driven first and foremost by those things he viewed as crucial to Ngaati Tiipa autonomy and wellbeing. Kukutai was an articulate and well-educated leader of Ngaati Tiipa. Waata was governed by principles of rangatiratanga (chieftainship), mana motuhake (independence) and loyalty to Ngaati Tiipa and to the whenua. He was deeply religious and courageous and was an entrepreneur who sought to protect his people by securing economic independence. This thesis shows how he negotiated colonial structures by forming strategic alliances, and in the process led his people through one of the most turbulent periods in New Zealand history.  

Waata was an enigma shaped by loss, vision and hope for a new future in extraordinary times in New Zealand’s history. Waata was a polarising personality who held fast to his life principles. He withstood immense pressure from other Waikato chiefs during the Waikato invasion. During the Waikato War Waata was most active, carrying letters, food and supplies to colonial soldiers and earned himself and his tribe of Ngaati Tiipa the label of kuupapa. While Waata was not the only ‘friendly chief’ during colonial times he has been the most pillorised in Waikato. Seemingly ignored by many historians is at the same time Waata ensued that Ngaati Tiipa land was never invaded by the colonial troops. Waata’s actions protected his people and his land and maintained his mana motuhake, his sovereignty over his district.

text: Waata Kukutai: Rangatira o Ngaati Tiipa 1822-1867 This thesis examines the life of Ngaati Tiipa rangatira Waata Kukutai (1822-1867), and critiques historical perspectives that have narrowly identified him as merely a Kuupapa loyalist. This study argues that Kukutai’s choices and leadership were driven first and foremost by those things he viewed as crucial to Ngaati Tiipa autonomy and wellbeing. Kukutai was an articulate and well-educated leader of Ngaati Tiipa. Waata was governed by principles of rangatiratanga (chieftainship), mana motuhake (independence) and loyalty to Ngaati Tiipa and to the whenua. He was deeply religious and courageous and was an entrepreneur who sought to protect his people by securing economic independence. This thesis shows how he negotiated colonial structures by forming strategic alliances, and in the process led his people through one of the most turbulent periods in New Zealand history.  

Waata was an enigma shaped by loss, vision and hope for a new future in extraordinary times in New Zealand’s history. Waata was a polarising personality who held fast to his life principles. He withstood immense pressure from other Waikato chiefs during the Waikato invasion. During the Waikato War Waata was most active, carrying letters, food and supplies to colonial soldiers and earned himself and his tribe of Ngaati Tiipa the label of kuupapa. While Waata was not the only ‘friendly chief’ during colonial times he has been the most pillorised in Waikato. Seemingly ignored by many historians is at the same time Waata ensued that Ngaati Tiipa land was never invaded by the colonial troops. Waata’s actions protected his people and his land and maintained his mana motuhake, his sovereignty over his district.

year: 2020